"Are you gay?"

I don't know if anyone has ever encountered such a problem like this: So you meet someone, and he seems pretty cool and stuff, but in the back of your mind you have a burning question...is he gay? Well, so I've actually came across this a couple of times. No joke. I feel like it's actually offensive to ask a straight guy "are you gay?" Don't you think so? I don't know maybe it's just me then. So anyways, I met this guy that I guess you can call him a friend or maybe aquaintance? I don't know, I'll consider him a friend cuz he seem pretty darn nice. He's always the first person that smiles at me every morning. LOL! Anyways, so I don't know what it is about him that makes me think that he's not so straight. So I was just looking at his tumbr that had "ex-gf" and "I miss him." So the next thing I came up with is he's bi. I don't have anything against gays or bis or anything of that sort. In fact, I support it strongly because I have a few gay friends and they're awesome. HAHA! Honestly, I'm just a pussy to ask him staight up, but curiosity kills the cat. Help? LOL I don't think I'm interested in him right? O.o