Okay, so next week I think my partner will be on her period. I want to have intercourse with her. What should I know? Will their be lots of menstrual fluid to the point where I will need a towel? I read that having intercourse on a females period is completely natural. I was wondering if I could use a vaginal contraceptive film for protection or if I should just use a condom? I guess the two things I want to avoid is having a huge mess on my bed and catching a STD. How should I check to see if someone has a STD? Will I see markings around the genitals? I always ask but I know people lie.