I think you should be examined by a gynecologist to make sure everything is okay. There is a condition called 'vaginismus' where a muscle tightening occurs making intercourse very painful and sometimes not possible at all - but I don't think this is your problem. I think your difficulty comes from not having the right partner and being ready for sex - meaning you admit you actually didn't want to engage in sex. This would automatically make your body unresponsive - not lubricating naturally. The next time you engage in sex - make sure it's with a very patient and gentle partner. Use good lubrication and you control the whole sexual experience - when, which position and how. Don't have sex if you don't want to and pick a partner who is gentle. Best of luck and I hope this helps.

** I didn't realize you are only 15 - you're too young to be having sex or drinking.