Hi Tiff, and welcome here

Yes, the best thing is to speak to a professional, or even two if you think one is biased.
You said you wore your mums clothes...well, do you like the clothes more, or the fact that you could be a woman yourself, no matter what clothes there are?
Do you want to be thought of as a woman, or just like the apparel that goes with it?
For transexuals, I think they want to be accepted as women, even if it is in t-shirt and jeans, it is not important.
But I could be wrong

For work, many people do it slowly, it does not have to be man one day, and woman the next.
Take your time.
When you are sure, tell your manager at work. They should know, or can find out your companies gender policies.
See your gender therapist, see your Doctor, see a psychologist, and see how you feel.
Whatever happens with you and your family, show love, and be happy in what you do.