What is this!!??

Hi i really need some help, so i had unprotected sex with a guy i obviously really trusted and a week or so later had really bad itching but never thought much of it until now, so this was 2 months ago now we slept together and i have only recently in the last 3 weeks or so had these symptoms. i have a flat red ( sometimes itchy ) rash around my vagina which seems to fade away every few days then reappear, also found quite a large ulcer to one side when i had a proper look which seemed have healed up a lot but now i have a few smaller looking ones on the other side! im really really worried and i feel sick to my stomach thinking its herpes and its putting me in a really bad mental state and honestly dont think i could carry on living if that was the case. i havent asked the guy because im terrified, i have an appointment booked to have my iud removed in a few days so i will definitely have it looked at then but until then im hoping i can get some answers that may ease my mind from here :frowning: