I wouldn't worry about the birth certif., I have never been asked /seen mine, don't even know where it is. I think that's more of a formality, DL, SSA, and passports/citizenships are the ones to go after. I tried to find that site I mentioned, but couldn't, though I'm pretty sure it would pop up if you tried "transgender/transsexual/resources/therapists" in the search engine... play around with any combinations of those words...They are a group, not a specific individual, like the therapist you found (he might work out for you) and you go through steps, like you have to send in photos of yourself, etc...
Wish you luck, let us know how it works out.