Are you sure it's him and not your vaginal secretions? Maybe the sex is a bit rough and causing you to bleed a bit, and it seems as though it's in his semen.

If there is blood in his semen, he needs to see a doc.

Were you a virgin before you started having sex with your boyfriend? If so, the bleeding could be due to the breaking of your hymen...although I wouldn't think it should still be bleeding. Like Georgia said, it may just be a little irritation inside you that's causing it. If you're worried, consult your doctor. Good Luck!

I would think it is most likely from inside of you. Is your sex painful at all? Is it close to your period starting/just finishing up?

If when he masturbates there is no blood in his semen, but it seems like there is blood when he finishes in you, I highly doubt it is in his semen. Go to a doctor if you are concerned, though!

not all virgins get thier hymen broke
and you can have your hymen broken even if youre not a virgin. your hymen can also be broken by exersize,masturbation and other things too

i agree with georgia. it may just be your vaginal secretions. do you feel a little irritated? if you feel pain and discomfort i would go to a doctor to rule out an infection. if not you may be having too much rough sex or you may be super sensitive. are you too dry during sex? not enough lube can be a problem. if all this doesn't apply and their really is blood in your boyfriend's sperm i would see a doctor asap. that doesn't sound too good but regardless i think the both of you should get checked out. better to be safe then sorry.

I used to have bleeding a small bit during sex and sometimes alot after sex. I ended up having a scope put into my uterus under general anaesthetic and the doctor found I had a heap of polyps in my uterus which were giving me pain during sex and the bleeding. It is currently being tested to make sure it wasn't cancerous. You should see your
doctor and get referred to a gynecologist.