[Potentially NSFW?] Vaginal bleeding during & after intercourse?

The last few times that I’ve had sex, I’ve noticed quite a bit of bleeding, during and for a day or so after. Last night it was so bad that we had to wash his sheets. I’ve also noticed a bit of pelvic pain during – it’s not terrible pain… I can usually just brush it off, but I think it’s important to mention anyway. Is this something I need to bring up with my doctor? Is this urgent? I’m really embarrassed about it, and I’ve never had a pap test. I am 20 years old and I’ve only ever been with one guy. What could be causing this? I’m really afraid that it’s cancer, since I am a cancer survivor, and I’m freaking myself out.