My boyfriend 18M has been acting like a child and I 18F dont know what to do?
My boyfriend 18M and I 18F have been together for about 3 months but we've been friends for about 3 years prior to our relationship, Ive noticed a complete switch in his behaviour and im not sure what to do about it. He is a man child in my eyes. I care a lot about my boyfriend and other than these aspects he is the healthiest relationship I've ever been in. Ive noticed that the way he acts is more like an 8 year old than an 18 year old and it's sent me into literal fits of pure rage. I have to give him constant reminders about dates, times, hygiene, respect, responsibilities, tone, reactions etc. Mainly the things you'd have to teach a child not a grown man, his behaviour is like he's never had a single ounce of responsibility in his life. For one example I have 6 cats and one a few years back got outside one time and passed away not entirely sure how but it happened, he knows I care a lot about my cats and their wellbeing. I STRICTLY tell him I need him to shut doors and be quick about leaving the house because 1 out of 6 of my cats are literal escape artists but besides that one time he was staying over at my house (my parents house because we both still live with parents) and he had ordered pizza, my cat was in my room which is right next to the front door and he carelessly opened the front door and my cat got out, which I can understand mistakes happen but he left the door open while the pizza person was there to tell me that my cat got out and as I was freaking out a bit and grabbing any bag I could find to attract my cat back he comes back in and I leave the room for a second come back and the front door is left WIDE OPEN while he's sat back in my room eating a silce of pizza, not a single care in the world or any offer of help just sat there eating on his phone. so I say " im not talking to you" as I walk out and spend 5 minutes chasing my cat down he walks outside pizza still in hand and I was like "thank god he's gonna help me get my cat back", no. He literally walks right passed me and down the street like a literal child trying to run away because his parents made him mad. I thankfully got my cats back inside and I check life 360 (an app you can see where a person exact location is) and he's halfway across the block so I call him and I say "can you come back its 1 in the morning" and its the most childish petty way he says "No." so im on the verge of just bawling telling him to just come back and he does and I just bawled the entire time when he came back because how can you act that way and think its okay? there was also this other time where we were out with my family and we didn't have our seatbelts on in the back (we were leaving a camp ground) and my mom of course was a little upset about it and said to put our seatbelts on and so we did, she then reminded him that he was 18 and if police pulled us over he would get in trouble and his response in the snarkiest tone was "well then I guess its not your problem then" TO MY MOTHER. Ive communicated with him multiple times about how he also relies on people to do things for him rather than him be a big boy and do it for himself. He relies on his parents to do his laundry, remind him to clean his room, buy him everything. For another bit of context I grew up in a household where it was "figure it out yourself thats your responsibility" so I became very independent and get incredibly frustrated when people act like its their first time on earth. I've had to remind him multiple times if you need something now that you're 18 you have to figure it out yourself because parents are busy and others are busy and he still makes excuses for it? he lives 30 minutes from me and usually has his dad drop him off at my house and recently his dad was feeling sick and couldn't drive him and then he also tell me later on that he was told by his dad to clean his room so that he could go? like dont you feel a bit embarrassed about that? his room is a literal pigsty btw. If we have to go somewhere together or be up early for something I have to fight with him to get up because again in his world these responsibilities dont exist. he does everything last minute resulting in him forgetting everything and I have to remind him to do it. Another thing is when I have an issue with how he acted or something under the million of things I listed his first and only line of reaction is to say "no I didn't" or he will bring up something so irrelevant to the initial issue just to prove himself right like Eg. "you did this so I did this" thing and I have to remind him that it doesn't take away from actual issue at hand and I can't help but be reminded of a child not knowing how to take responsibility for something. Rather than growing in this relationship I feel like he's regressing backwards. He does not like to listen to anything I tell him at all, he has a scab on his face and it kept bleeding because he keeps picking at it and he's got strips of blood on his hand from wiping his face and I tell him to wash it and he just doesn't. I tell him if you're complaining about chapped lips put this on, he doesn't. I tell him you need to get up and get ready to go, he doesn't listen. he got me gifts for my birthday and not a single one was here in time for my birthday because instead of making an effort to just go out and get things he just ordered everything a week prior to my birthday. He is all about convenience rather than get It down before its due. I've communicated to him that I've had to parent him more than be his girlfriend and his was response to it is "well you get frustrated at me" yeah I do because you are acting like the most low effort person. he doesn't take care of himself properly. Im sorry if this is all over the place but I just needed to tell someone because I feel like I am literally crazy for focusing so much on these things, I know we are considered young but he is old enough to do all of these things for himself and he just doesn't. I just need some reassurance and advice on how to deal with this and whether this is even an issue that can be fixed.
EDIT: he also does have insane jealousy issues as well that you genuinely would only find in younger children and their first relationships, once I laughed at his friends joke in a group chat and he told me he didn't like that and not to do it again.
EDIT x2: I am not looking for judgement genuine help and this is my first time ever posting on reddit so please save the comments.