Feeling weird on one side.

So lately I've been getting pain/cramps on one side of my body, and my back hurts as well. I've also been spotting but haven't gotten a full on period in almost a month, although i am on birth control and that doesn't stop my boyfriend from pulling out, lol. Anyways i feel like i might have a cyst or a ectopic pregnancy but I'm very unsure.. Anyone have any advice they'd like to put out there? Please.