Blood during sex!

Rhi • Hi, I'm Rhi. I'm 20 years old and my hair colour changes with the wind. Currently have no children but a partner of four years. When I'm not playing video games I have my head stuck in a book.
Nearly every time me and my boyfriend have sex, there's a lot of blood involved, to the point where if there's none at all we're both surprised. There's not usually any pain but sometimes afterwards I get cramps. My doctor doesn't seem to be worried, but should I try to get tests done anyway?