Why do I suck at sports?! I don't know!

And it didn't bother me at all before... just when I was picked up last for any sports team, but that was a long time ago. Anyway, the other day the doctor told me to do some kind of excercise. People have given me that advice several times but I've never considered it until now. The reason? It's very simple, the doctor explained to me that excercising would make me happy....blah blah blah. The thing is that maybe he's right...probably, since he's a doctor. And I'm just tired of crying everyday, so I'll give it a try. So, now I have to do some kind of exercise and I don't even know where to start, I really suck at any sport. And I mean it, I've tried everything but nothing seems to work for me...just ballet but that was a long time ago and now I'm too old. I don't even know somebody who sucks as much as I do in sports...I'm slow, I'm afraid, I'm self-conscious, I'm weak....And I don't even smoke!!!! What the hell is wrong with me?! Seriously!

Any advice would be appreciated.

XoXo
Gaby