I think we all have had these thoughts from time to time.
Let's reframe the question:
Not Feminine enough? For what?
What measurement of femininity are you using? If you are comparing yourself to how others look, who specifically? There are women who look more manly than some men, and some men who look more feminine than women. Humans come in all shapes and sizes.
If you drill down to what is actually triggering these thoughts, you may find the area that you want to improve. Bigger bust? Voice training? Mannerisms? Makeup skills? Clothing? Walking style?
Each of these can be things that can be addressed, but remember, they are only appearances. There is no standard for what a Real Woman™ looks like. Make a list and take it with you to your therapist. If it is something that really bothers you, make a plan to work on that.
In physical appearance, I don't think I am all that feminine. Hair, makeup, jewelry, and clothing help. But I am also at peace with who I am because I refuse to be held to other people's standards.
Be patient with yourself. Work on what needs work, and learn to accept that no one is perfect.