Im not sure if i can shed complete light on your boyfriends excitement but it sounds a lot like mine.

What gets me excited is the Threat the idea that a woman WANTS to do it to me not so much that i want it done. Sex and Desire are crazy and complex.

My fetish come from my first few sexual encounters the girl was really hot and in to some bdsm. she tied me to the bed blindfolded me and started to play with me. she told me how much she really hated that men had cocks and was going to give me a test. if i passed then we could have sex for as long as i wanted. if a failed she was going to bite off my cock.

i figured she was playing and agreed to the game. she started to sly with me more and got out some baby oil. i had never used lube and was really suprised at the difference it made after about 5 mins it was getting a bit hard to resist. then she wrapped both hands around me .... my brain suddenly realized why men in pornos make such dumb faces .. i bet i looked like all of them combined ... needless to say i lost the challange and made a mess. as the after glow set in i heard her say Such a pity i was looking forward to having more fun. then i felt Teeth. she took me in to her mouth and bit down hard. Ohh god the Fear shot through me like a rocket. i could not breath could not make a sound i pulled at the ropes and tried to get free. after what seemed like an hour she released her grip and slowly slid her mouth off me. the feeling of her tounge and mouth on me after the pain felt like static shocks all the way up and i came second time. to this day i have never felt any thing quite like it. but it let a lasting scar.

The idea of having a woman threaten me or challange me with the chance of loss or pain. ( or the damn chasitity device ) will make me mindlessly aroused. i dont particularly like the pain some times it fun and good for enhancing the pleasure but over all just the fact that the woman has made the threat. Thought it up has said it to me is enough to send me wild.

Ask your boyfriend if he knows shen he first discovered he liked this kind of play. ask him what it makes him feel and what part arouses him the most.