What should I do?

I’ve known his guy his middle/high school and we were friends for a long time but in high school freshman year I got this boyfriend who wouldn’t let me have guy friends so I couldn’t really talk to my friend I was with that guy until May of senior year so I recently reconnect with my friend on thanksgiving when I told him happy thanksgiving knowing he wasn’t home for the holiday because he is in the army and stationed out of state and on thanksgiving we about shared that we had crushes on each other so we started talking and still are I trust him and everything but he stated he still talked to his ex and I really didn’t like the fact he still talks to her because who still talks to their ex’s he said he would stop if I want him to but he is so far away how would I know if he isn’t and we would FaceTime every night since 11/25 but lately we haven’t and we don’t text as often either but I understand because he is in the military but he is coming home on the 21st and we are going to stay with my cousin and we were planning on having sex but as of right now I don’t want to until I know we are serious about each other because what if we don’t work out I don’t wanna ruin our friendship

what should I do? should I tell him when he gets home? I shouldn’t? Just get straight up with him?

Honestly I want to be in a relationship

I want a serious long term relationship

UPDATE-

I’m in Texas and he is in Georgia

He says they are just friends

They broke up because she cheated