The Verapamil you were taking is a blood pressure medication, and there are many other medications that can be taken for prevention. There are also drugs other than "triptans" which can be taken to abort a migraine when you feel one coming on. I looked up the Verapamil, and there are so many things that it shouldn't be combined with, you probably ran into some interaction without knowing it. Anyway, time to find something else. Plenty of other choices out there. I personally use 200mg Topamax.
The first thing you need to find is a new doctor. No professional physician would throw their hands up in the air and tell you that you are crazy and are imagining the pain. KICK THIS DR TO THE CURB! You may want to work with General Practioner and a Psychaitrist(strictly for medication purposes) for a while. Forget the Neurologists with all their fancy tests and crap. Good GPs are underrated. Most good preventative medications can cause some depression, if you didn't already have some from the headaches. The Psych can hook you up with something that will work with what your GP prescribes for the migraine prevention.
As far as Pain Clinics go, I've found that they want to keep you on the least amount of medication possible, and were absolutely no help when it came to dealing with migraines. You get terminal cancer, they'll hook you up, otherwise you're screwed. Pain shots from the ER work, but pretty soon they will consider you a frequent flyer and not give you the current medication you are receiving. As far as Phenergan goes, you can get a prescription for it, not injectible, but in suppository form (oooooooh, what fun....not).
Think I covered most of your questions. I'm going to go bury my head under something heavy and dark now. Had a real headbanger for six hours now and my preventative doesn't seem to be working any more. Geez, I'm so screwed.
Best wishes and lets us know how you are doing.