Improve 560 credit score
I'm a master's degree student with no current income. I messed up my credit score by not paying the credit card for about 5 months, although they're currently only showing two missed payments.
I have been paying the card promptly since November so I've had about seven payments. According to my credit score, it's low because I don't have many credit cards.
How can I improve my credit rating as once I do get my degree I'm going to want to buy a car and probably rent an apartment perhaps with my girlfriend.
Does it make sense to open another card and pay it just to have it on my record?
Is there any point in calling the card company and asking them to remove any negative comments on my card sunce I've been paying for seven months?
I'm not paying a total amount. I'm paying about $100 to $150 every month on the balance of about $800.
Any advice appreciated. Thanks!