u/chihuahuao

so me (16F) have been in a relationship with my bf (17M) for over 9 months now and in the beginning of the relationship he usually came over to my house but lately i have been spending more time with his family (mostly his mom since his dad works abroad) and his older sister. i have noticed that both him and his sister often hug and just are affectionate towards their mom which isn't that unusual however when we went to the lake he kinda gave me the ick when he was begging his mom to put on sunscreen on him like on the face and body everywhere and it was kinda weird he acted like a baby like he couldn't do it himself and it was uncomfortable for me but i kinda just brushed it off. after we came back from swimming in the lake his mom had a pillow between her legs because she was reading a book and he laid down on the pillow and i was laying alone. he constantly picks on her as a joke and hugs her and you can see he loves his mom very much. when i started feeling uncomfortable i went to sit on a hammock further away and just sat by myself because i knew i was just overreacting but it keeps sitting in the back of my mind. just for context in my family we rarely hug like only when one of us is going away for a few days and even then it is weird and neither of my parents are very affectionate even between them so i think thats why i feel that way but i just wanted some insight. i just feel left out because im his girlfriend but he keeps cuddling up to his mom and i know thats his MOM but if im next to him i feel like he should be cuddling with me. i tried talking to him in a very respectful and calm way and just told him how i feel but assuring him i don't want him to change his relationship with his mom but only to get some reassurance and so i don't build up any resentment however it changed into a fight and he immediately responded with a message saying he wont ever change how he acts with his mom that it isn't negotiable and that im weird for even having a problem with it even though in my long message i explained that i don't know how a sons relationship should look like with his mother and i don't have a problem just that it rubbed me the wrong way. should i be worried or is it just my problem because of how i was raised?

edit: we talked it out one more time and everything is fine now. he told me by himself that he will respect my boundaries and won't act the way he did in the sunscreen situation. i assured him that i dont want to change his rls with his mom and that its not my business but he can always count on me and should remember that when im with him he can also ask me for anything. i do think i overreacted but my feelings are also valid and im glad we resolved it. thanks to everyone in the comments it was also very helpful