Scarleteen

So I was having sex today with my girlfriend during the last or second last day of her period (been 5 days since she started). She said she was spotting earlier before we had sex.

I had a condom on, but during the sex when we changed to cowgirl position she took off the condom and we continued having sex without a condom. Shortly after that (5 to 7 minutes), she said I was too deep and it felt like I was hitting her cervix. So we stopped and she got off, then we saw that my penis was covered in her period fluid (blood?) and there was a piece of clotted blood or uterus lining.

I checked the condom she took off and there was no blood, so maybe me hitting her cervix caused her period to go from spotting to full flow.

Anyways, should I be worried about anything like dying or contracting something? As a note, we have tested and we are STD/STI free.

Menstrual fluid, in itself, is not at all harmful or dangerous.

If the person has an infection which is blood-borne or carried in other bodily fluids (for example, cervical fluids), then menstrual fluid can carry and transmit that infection. Because menstrual fluid contains blood, contact with menstrual fluid has a similar risk level for transmission as contact with another person's blood - higher than contact with just cervical fluids. However, infections - including STIs - don't appear out of nowhere; someone has to have an STI in order to transmit it to someone else. So, if you and your girlfriend both tested negative for all STIs and haven't had any sexual contact with anyone else since then, there's no STI which you could transmit to the other.

Similarly, if neither you nor your girlfriend have any illness which would make contact with the other's blood (for example, by accidental cuts or injuries) any cause for concern, then coming into contact with her menstrual fluid is no big deal.