This happened when I was a young 20 year old male. (45 now).
My friend Cindy lived in an Apartment building. I stopped by to check out her new place, and knocked on the wrong door. an older woman answered (31) and she was tight! Small perky boobs, blonde hair, nice small ass. About 5 feet tall. (I’m 6 foot). Gorgeous smile.
I asked for Cindy, and she said Cindy lived downstairs. I apologized, and went downstairs. No answer at her apartment.
The lady from upstairs headed out around now, so I decided to sit and wait for Cindy. She knew I saw stopping by and was probably just running behind.
About 30 minutes later the woman from upstairs came home with bags of groceries. She was clearly having problems so I offered to help her out. She said her name was Cathy.
Once in her apartment, we started talking. Things got flirtatious, and talk led to oral sex. I leaned over the table to kiss her, and she kissed back, we started moving towards her living room and before long, both of our pants were off and I was fucking her doggy style. Then I noticed it… BLOOD. Seems Cathy got her period. We stopped, she apologized and since some blood ended up on my underwear, she went to wash them with my shirt. (Shirt also had some). She tossed me a towel, and I wrapped it around my waist.