Possibly pregnant!?

So for a little over a month now my boyfriend and I have kind of given up on pulling out every time we have sex ( and before you say it I know it isn't the most effective form of birth control but oh well better than nothing) And I know for a fact he came in me a couple time while I was on my period and a couple times the week after. I am suppose to start my period again in a week but for the last week or so I have been having the worst cramps ever. Way worse than the cramps I get while I am on my period. I was talking with my best friend who is pregnant now and she said that was one of her signs when she got pregnant. So I just want your input on the whole subject. And please don't be negative.