STD ?

So my boyfriend has openly admitted to cheating on me, we had sex the first time last week since he started acting different and I think he gave me an std after saying he had been checked , my discharge is white and runny. I got checked less than a month before we had sex again and he’s the only person I’ve been with for years (we’ve been together for 4) I just don’t wanna spend money going to the doctor (I don’t have insurance) if it’s nothing. PLEASE HELP !