Two sex questions: bleeding & swelling

Jess
These questions are separate, I would really appreciate any insight and advice please. 
My boyfriend and I just had sex. I always got to the bathroom after to pee. (Doc recommended to avoid UTIs). When I wiped I noticed a small bit of blood. Bright red not brown like leftover blood from a period. Does anyone know the causes? 
Second question, most times after we have sex one side of my vagina gets swollen (my right) and a bit sore. It has with other partners, not just my boyfriend. Even with lots of foreplay it still swells up a bit and is sore. Due to it swelling, that labia is slightly larger than the other one. Does anyone know why? What I can do to avoid it?