Is it normal to get my period and still be pregnant?

So, this is the problem: about a month and a half ago, I got involved with a guy and we had sex. He did wear a condom for most of the time but there were a couple of times when he did not wear one but only for a really brief period of time (when I told him I wouldn't go forward with it if he didn't wear one).

Setting aside how much of a douche he actually did turn out to be, I did end up thinking about the possibility of being pregnant. I had just finished my period when I had sex with him and so I waited around for my second period, which came a couple of days late but did eventually happen and the flow was as heavy as usual and it lasted the usual amount of days.

That made me feel a lot better about myself but lately I've been feeling a bit strange: I have a lot of stomach aches and gas and I don't know what's going on. I don't have any Simpsons of pregnancy like swollen boobs and morning sickness but then again if I was pregnant wouldn't I be way too early into my pregnancy to actually have these symptoms?

I know there are stores of women who get their period and are still pregnant and I'm afraid that might happen wit me. I know I'm probably overreacting and all but I am super scared and don't have enough money at the moment to get a pregnant test (they're really expensive around here).

What do you guys think?