Advice Needed

Ok, real life right now!
Help/Advice please!

I've got a best friend at the minute who I've known since September and the start of college, which was a big new start for me. He's my first male best friend and I feel like I can tell him pretty much anything from drunk texts at night to long bus journeys home.
We play fight and mimic each other and it's always a good laugh.
He's pretty much adored by everyone even though he's genuinely a bit of a screw up who's always looking for some fun. He takes care of me too especially when my diabetes is an issue.
So what could be better in a friendship?

Yeah, there's the problem :D
I think about him loads and I miss him when he's gone. But not in the same way I miss my other friends.
Lately I even get a twinge of jealousy when other girls give him attention or I know he's going to hook up with them.
It's even come up once or twice with other friends asking me do I like him more, which I've mostly denied unless very drunk.

A few months ago on a foreign trip I'm pretty sure he wanted to get with me but ended up in bed with another close mutual mate and kissed another girl I'm friends with.
It's pretty weird but I always laugh it off like one of the lads and keep my distance.

Trouble is I've started comparing other guys to him in my head. I want to go out with him but I know we're at different levels of experience and confidence. He also does some stuff with drugs that I'm not totally cool with but nothing serious at all. We're identical in intelligence and humour in a lot of ways also which has bonded our friendship.
We really are best friends, I don't want to lose that.

So what's changed lately?
He wants to drop out of our course which is one of the main reasons I couldn't get with him (five years that could potentially be super awkward) in the beginning. But he might stay too.
Ugh I don't know anymore how to make these feelings stop!

Help from anyone who's ever been in a similar situation would be seriously appreciated :)