It can be hard for some people to know whether or not they are gay, but it's important to remember that deciding you are gay is a personal decision and not a clinical one. Some people that have homosexual experiences continue not to identify as gay while others that have never had a homosexual experience and rather, just have homosexual.
I mean Richie and Eddie were always chummy in the book but I never saw it as more than them just having a lot of banter and being good friends. Did I miss something in the book or did King actually insinuate Richie was gay? In any case it feels like a bit of an undercooked character arc in the movie.