Can I be pregnant? Please help?

So me and my boyfriend had sex without a condom. I’ve been on birth control for almost a month now. I’ve never skipped a pill or anything. As we were having sex, I noticed a white sticky substance (probably cum, I’m not sure) dripping but he was positive that he didn’t finish! Is there a possibility I can be pregnant? I feel sharp cramps and my back is killing me! HELP!!!