i think i have an STI

so i was showering and i noticed i had some green discharge and ive been experiencing itchiness. i made an appointment to get checked tomorrow and im just certain i have an STI.

but how am i supposed to handle this? im 16 and im gonna be completely honest and say i haven't been safe or responsible. my bf and i do have a lot of sex and most of the time we dont use protection.

im guessing thats how i got the infection, but how do i handle this?

like do i tell him? and what do i say?

its a little embarassing for both of us but someone please help.