Lots of people make excuses, but if they really sat down and thought about it without any internalized transphobia they'd realize it's actually because they want to be a girl more than anything else.
It could mean that you're a guy, but it could also mean you are a trans woman with lesbian attraction. There are trans women who still have and use their penis in sexual intercourse.
If you feel like you want to be a girl and have an urge to do girly things, it's more likely to be the latter though.