First I`d like to tell you that there are many many guys and girls out there like you. And a lot people havent had sex or kissed or held hands until they are 22 or 25 or even older. It`s not that unusual at all. I have a friend who looks like a supermodel but has never kissed a guy. She too, is like you - tense. She also says she cant loosen up or start a conversation or dance.
Some people are just like that.
You cant change that overnight...
You have to take small steps... you might never be the guy who dances all night on the dancefloor (which is more than okay)but you can and you WILL (trust me) get more confident. You are still very young. It will get better over time.
I would suggest what Brutha said - take dancing lessons. In addition to learning how to dance it will loosen you up - you will get used to physical contact and having a woman that close to you. I think that will be very important. That friend I talked about - she once told me that when a guy brushed her arm, she jumped... I think it`s similar to you freezing on the dancefloor. You might think it`s silly and impossible but your body is not used to being that close to the opposite sex and subconsciously you just make a big deal out of it and freeze. You get all anxious and nervous and cant relax. My English is awful today, I hope you get my idea..
And once you learn to dance you WILL have women wanting to dance with you, really
It`s just such a joy to dance with a guy who knows what he`s doing. It doesnt have to mean anything sexual, it`s just SO MUCH FUN.
Ok, I know that you dont consider dancing fun and its not your thing but I think it will do miracles to getting you more confident and comfortable around women.
Trust me, this will work itself out eventually