how to have a sex talk with my boyfriend?

So, my boyfriend and i have known eachother for about a year or so now. we've been sleeping together for 8 months now...

Im into bondage & being hit & choked and all that freaky shit but he doesn't seem to be.

i have spent a lot of money on bondage stuff & hes never once touched it. (i bought it before we started sleeping together) he does know im into that stuff & always talks about tying me up and everything but when the time comes, he never does. and he never does down on me and forplay with him is kind of a joke.

im unbelievably happy in our relationship but the sex could be SO MUCH BETTER.

how do i talk to him about this without offending him or upsetting him?

im not / never have been one to express feelings easily in our relationship due to a horrible past relationship so this is a talk id usually never have with a guy but its bumming me out.