He might be wrong in the head. But a lot of 15-18 teen boys sex is something they boast about (not how long they last though!) and although he might see you as 'easy pickings' he could just be nice, he didn't try it on with you when he had most incentive to that's got to be a good thing right? I'm 15 and have a few 12-13 year old friends and frankly I feel more comfortable around them because they DON'T want to sneak off and make out in a bush. Be aware anyway, somepeople are just sick.