I could have written your post, all but the part about feeling like someone put a pillow over your face, and I don't have any neck problems. I too have always been a night owl - 3AM to 10AM is my ideal sleeping time. A few weeks ago I started staying up later and later, and now just about every other night I stay up all night. The next day I either manage to stay awake until 9 or 10PM and sleep until early the next afternoon, or I lay down for a *nap* that afternoon and sleep until 1 or 2 in the morning! It's driving me crazy, but I don't know what to do about it. I try going to sleep at a *normal* time, but I just can't - I'm not tired. I'm having major surgery next week and will be staying with my grandmother to recover, and everytime I stay with her I go to bed before midnight every night. I'm hoping that after I come back home I can get back to my regular schedule.
I suffer from major depression, severe fibromyalgia/CFS, and a few other health problems, but I had all of them well before this started. I'm in desperate need of a sleep study, but I have so many medical expenses that I keep putting it off. It sounds like you really need to have one too.