I don't know how much my input will help, but I thought I'd chime in as someone who's still kinda new to this too.
I realized that I might fall under the trans label over this last summer after doing a google search for penis envy and seeing that I wasn't the only one that felt this way. (I realize that's not really what penis envy it, but I didn't have a better phrasing for it) I've always felt more comfortable in guys clothes and when I first learned the difference between boys and girls, I wanted what they had. Of course, back then my friend told me that it was just that boys sat on the potty backwards. Imagine a six year old trying that. It didn't go so well. Haha.
When I first found this site, I posted a topic about my confusion, and got some good replies. But I jumped straight to androgyny when I felt the FTM term didn't completely fit. I've done a lot of research since then and I currently identify as gender queer, a little gender fluid (I still have some days where I'm happy being a girl), and transmasculine. I'm still pretty confused and kinda scared some days, but I've gotten more comfortable the more I've explored.
My first step was getting a packer (an STP since I've pretty much always been obsessed with being able to pee standing) and, man, did it make a difference. I loved it. I wanted to present more masculine, too, so I started out by getting a short, more androgynous hair cut but now I have a traditionally male haircut that I feel just fits me. Then I tried wearing button down shirts more than just t shirts and I find that I feel a lot more confident and comfortable in them.
So like others have said, I think talking it through with your therapist is a good idea. Remember to take it slow. Don't worry about not being trans enough or trying to fit into the view of what you believe being a "real transgender" is. Just be you. Do what makes you comfortable.