I wouldn't worry about your ability to get pregnant. It's only been 4 months. Many women have to try for longer than that. It could be that you are not having sex at the right time, during your most fertile timeframe before ovulation. But, if you do not want to be pregnant, you should stop playing russian roulette! If you keep having unprotected sex, you are bound to get pregnant eventually.
A UTI would not affect your ability to get pregnant, btw, because your urethra is totally seperate from your reproductive organs. And that feeling that he is hitting your ovaries, don't worry about it. I've felt that too and I have been pregnant.