I can't believe this, I felt so relieved yesterday after speaking to the dr about how I feel. It the first time I've mentioned to anyone what I'm thinking or feeling regarding my gender feelings... And it felt so good and relieving to have it sort of "out in the open"

I've had the best sleep I think I've had in years, but today the euphoric state I described yesterday has gone, and I'm back to thinking, what about family, friends. Have I made the right choice? Or am I pathetic?

This is so unfair.

What choice have you made?  To be honest with yourself and others around you?  This does not mean that you have to do anything.  You have simply acknowledged yourself to others, including your doctor.  There does not seem to be any cause for guilt or bad in that action.

I remember the euphoric feeling when I first opened up to my mom.  It lasted about 10 minutes before I went back to thinking that likely some form of insanity was in play.  At least it was no longer hidden though and that brought relief.

You will be ok and here you are among friends.

This is all common. The euphoria you felt was most likely a by product of all the adrenalin your body was pumping out before telling the doctor. You survived a stressful situation and were elated. Now that has settled down all the worries will come wriggling back - the real skill is in learning how to learn to cope with worries and fears and uncertainty. Part of that is understanding the situation with some perspective, you're imagining everything and that you have to deal with it all at once. That is almost never the case... for any of us who have chosen to transition every step of that journey was a new challenge, and some were larger than others, but they didn't all happen at once and often the whole process took years. So relax, you have plenty of time to sort things out - it will also work better for you if you can have support in that process (therapist or whoever)... the more the better.

It's perfectly normal to be unsure for a while. It takes time to come to terms with everything. That first doctor visit is intense!
If anything I admire your courage.