Lily - I can just give you my point of view.
For me, CDing is a fetish. You can look up transvestic fetishism. If you bf is similar then perhaps you might be put more at ease. I, personally, have no feelings of two selves - I believe I even have posted on the topic. There's just me. Sometimes, I'm "too feminine" but most of the time I'm just a guy. I was beat up most of my adolescent years for being a "f*gg*t" even though I wasn't - I even had a girlfriend. But those football jocks could sense just a little bit too much softness in me, I think - I've always been the guy girls said things like "I hate men, well not you - you don't count" - girls always trusted me with girl talk, changed near me and the like. They'd say I was like one of the girls but a guy - there was no CDing involved, I'm just further toward female on the gender continuum than most guys.
When I dress I'm just turned on. I don't feel like raising my voice and being "Stephanie" - but when I'm dressed I allow myself to act more feminine. So I can get it out - most of the time I'm busy pretending (out of habit) to be more GUY than I really am.
Here, on the forums - its a fun kind of roleplaying for me. Perhaps your boyfriend is more like me if he hasn't confessed a hidden self or introduced you to his dressed persona. For me, the name is unrequired - icing on a cake that exists just to be eaten real quick anyway.
Hell - I forced myself to come up with a name as a way of accepting this side of me. I found it very therapeutic. Like, by giving "it" a name, I could put "it" away when I was done. Compartmentalizing myself to gain control of the urge, maybe? (Kew? ;) ) And, just maybe, a bit of disassociating myself from the "problem" by giving it a name other than myself.
All of that is just me. I really hope that helps... I dug down on that one ;)