Wait to see if he becomes single. If he does than let him know your feelings for him, if the girl's moving she's most likely going to find a new Bf .
There's this guy that I've known since kindergarten. I get butterflies when I'm around him, my skin is on fire when he accidentally touches me. He has a girlfriend. But she's moving in July. Should I wait till July or keep my mouth shut forever?
You should say something now because you don't know that guy might have feelings for you too but he never said anything because he was with another girl
Best to tell him now before they move in together, coz if you delay it he might have kids and a family and your heart will be sore.