What are the chances of me being pregnant?

I'm eighteen years old and over the course of two months, my sex partner and I have had unprotected sex four times. He's pulled out in time every time. A few days after the first time we had sex, I got my period. A day or two after I got off of my period, we had sex and then had intercourse again the day after. Earlier this month we, again, had sex. My period usually comes later on in the month (during the last week or so) and I'm scared to death that it isn't going to come. I know that pre-ejaculatory fluid doesn't contain sperm and the risk of pregnancy is low if the male did not ejaculate inside the girl, but I can't help but worry. I haven't experienced any tenderness in my breasts or weight gain that anyone has noticed nor have I experienced nausea except for at night when I think about the possibility of being pregnant and I think that is just in my head. I did have a urinary tract infection and a few times when I wiped after urination, there was a tiny bit of pinkish looking blood. I read that its normal during UTI's but I've also read about implantation bleeding and I'm worried that it may have been that rather than from the UTI. The bleeding stopped and I got rid of my UTI. Basically what I'm asking is how large the chances of me being pregnant are, if I should be worried, how to go about telling my partner if I miss my period and where to go/how much to expect to pay to have a pregnancy terminated? I know that its a lot to throw on you at once, but I'm very scared and unsure of what to do. He's the only sex partner I've had and I'm terrified. I just got out of high school and I know I'm far from prepared to care for a child. I can barely take care of myself let alone a baby. Yes, it was stupid of me to have unprotected sex. No, I'm not on birth control. I never thought I would need to be because before I met this man, I was absolutely positive that I was a lesbian. I'd appreciate it if whoever answers this could answer without passing judgement on me.