How to teach my bf.

So my bf of 3 years is great i love him. However my sexual tastes run way darker than his. dont get me wrong the sex we have is great but....he is always worried about hurting me. I keep telling him i have a high pain tolerance to go harder/ choke me / spank me / bite me.

Nothing make me cum harder than when i can make him lose control and he viciously bites my neck. How can i get him to let go all the time?