Can you be pregnant and still have regular "periods"

I know that bleeding during pregnancy isn't a period. But that doesn't change the fact that I've been getting regular "periods" where I bleed like I would and at the time of my scheduled period, but I have the emergence of a baby bump as well as pain in that area. Maybe it's just because I'm sexually active but not on birth control (I use condoms) that I'm always worried I will somehow get pregnant. But this weird belly plus the constant stomach ache is really freaking me out. What's happening?