First of all, I don't know what you've done in terms of progress towards your transition, but thinking about it and starting to do something are 2 different things. Therapy, as you probably are already well aware of, is the first step. The thing is you need to take it one step at a time.
As for upsetting your parents, from what I remember, transition will do that. It upset my parents and they still haven't calmed down about it. I imagine one day they may start treating me with a little more respect, but until then I can't really do anything about it. My point is, if something as minor as my parents being upset had stopped my transition in my tracks, I wouldn't be living as a woman right now. In a way, it really was a non-issue, because the looming threat of death was so eminent and if I had listened to them, then I probably wouldn't be around today.
If I remember correctly, you are not currently living with them, so it's not like you're in danger of being kicked out, but obviously you know your situation far better than I do. Anyways good luck.
Melissa