Hi Izzy
If the 1970 in your nick is your birth year, let me tell you that age alone is not an issue, and there is plenty of scope for you to be the woman you want to be. The journey from here to "there" takes some time, effort and money, but it is worth it.
There will be ups and downs, and there are no "correct" feelings. The self-questioning is, frankly, a good thing, as it means you are looking at a complex issue in detail, and many of us ask these questions at the start of our transition. As you advance, everything gradually becomes easier.
Keep an ear on that little internal voice that only you can hear. If it says that it's unhappy on a given day, park it out of the way. If it starts to become insistent, listen to it: slow down, understand what it's trying to say - this is not a race - and correct things.
I hope this helps. Good luck!
Julia