I had the exact same experience. I ended up sleeping with the guy I had been crazy about for 5 years, who I thought was "the one", and it was so awful it cured me of any feelings I had for him. He became my best friend (and no, I didn't "friendzone" him, it was mutual), and he was my Man of Honour at my wedding last year. Best decision I ever made.

Performance anxiety maybe?

First time doesn't count , you need to Rey it out one more time!

Having sex with a close friend of the opposite sex is never a good idea

Try next time it will be better!

Doesn't matter had sex

If it was the worst sex then you obviously dont love the guy

Fyl, but sometimes it takes a little practice to get in tune with eachothers bodies. If you're going to have sex again, tell him what you like and what you don't. If this guy is everything you think he is then eventually the sex should be spectacular.

You guys don't know each others likes and dislikes. Talk to each other and it can only get better from there.

Not all first times are that bad ... My first time wasn't mind blowing or anything, but it wasn't bad at all. It definitely wasn't as bad as some people told me it would be either ... The second time turned out to be amazing. Every experience is different.