Hey there, in my opinion u really need to spk to your girlfriend again, and really make her listen and undertand what you're going through. Tell her you're fears of her not wanting you. Maybe there is a reason why she isn't wanting alot of sex, there could be a reason for it. Plz spk to her and express you're feelings. Thats the only thing u can do. Oh and btw, dont pressure her for sex, that will only push her away even more.
Tossing around different possiblities here. Males reach their peak right where you are now while females tend to reach their sexual peak in their 30's. Or she might very well be interested in another relationship. Or is she under alot of stress from her school or work lately? Is there things going on in her personal life with family?
There are tons of reasons why her sex drive could be decreasing. If she's on new medication, switched/started/ended birth control, stress, loosing interest in the relationship, just not in the mood.
Don't pressure her. If you do, she could very well begin to regret you and leave the relationship. There is nothing worse than having somebody nag at you for sex when you just really don't want it.
first thing you need to do is ask her why only sex 3 times a month. if she is worried about getting pregnant, have sex with the lambskin condom. it still gonna feel like bareback sex, well very very close.
I think you should be patient with her some more. A lot of women want to know that you not only want them for the sex, you also want their company, and their friendship. Pls don't pressure her because if you do, you may lose her, as she'll be thinking that's all you want from her, sex. I suggest you give her time, and make an effort to put more into the relationship other than sex.
All the best. :) xx