what is that stuff that comes out after he comes inside me?

when me and my boyfriend have sex, sometimes he comes inside me. and then a couple days later this stuff starts to come out and it really smells and it only happens when he comes inside me. is that normal or should i see a doctor?
well it does come out directly after, but then a few days after that again or something. then if it is semen, does that mean i could still be pregnant cause for some reason i havent been getting pregnant. recently we did that and i havent gotten my period, but im always irregular and there's no signs of being pregnant or getting my period! but this was just about 2 weeks ago. i took a test just to see and it said no. im going to wait another week to take another.