hi, my girlfriend had her period 13 days ago, and a few hours ago we had dry sex and i ejaculated through 3 layers of clothes: my boxers, her pyjama pants and her underpanties) it definitly went through her pants but i am not sure if it went through her underpanties, the stain on her underpanties could have been from her fluids... she washed her vagina 5 mins ;ater and changed her clothes. my question is could she become pregnant from dry sex with 3 layers of clothes on??
No she can't be pregnant.  Don't worry. Sperms cant penetrant 3 layers.  But it's my suggestion to use protection next time.