im really concerned if u can get an std if a guy ejaculates on your underwear?

Hi,
No, you get an STID by having intimate sexual contact with someone who already has the infection. The infection is spread by skin to skin contact with an infected sore( with genital herpes) and having oral, vaginal or anal sex with an infected person. Your underwear protected you. It is very important to know if a sexual partner has an STD. Awareness can save your health.
Maryann