Most Helpful Guy
Personally, I think light pain, relating to intimacy with a lover, done for the right reasons, can be good. I realize that this is not strictly what you are talking about, but as for doing it with your boyfriend, maybe look at the Why's of why you are doing it and enjoying it.
You mention that pain for you is like a drug addiction, that it takes you to a happy place. This suggests to me two things, one or the other, or possibly both: I would imagine you know about the endorphins, adrenaline, and other chemicals which are usually released when pain is felt, that make you feel good. I don't think you do it just for this though, not like someone who cuts just to feel good.The second idea that came to me, purely guessing of course, is that maybe a part of you feels a psychological need for punishment, for whatever reason, and thus, you may feel the need to punish yourself.
Moving on from that, I think maybe you could ease into this kind of thing by starting with something like some simple dominance or coercion techniques from him, getting him to be more dominant and showing him that you like it like that. Getting him to start with things like pinning you, or spanking you, and then moving towards more physically painful things that you like, may work, as he may be more accepting to get there in small steps than a big leap to causing you pain. To cause pain to a lover, even for pleasure, usually takes a strong bond, a certain level of trust, or a particular mind type (that would be, the type that likes to cause pain).
Or, failing in this, even say directly to him what makes you feel good, if you think he'll be okay with it. though I would hazard a guess that a certain amount of trust and acceptance would be needed if he did not have similar desires himself.
But then, these are all only my opinions...