Never forget that when you get out of your parents influence, you can be yourself more than ever before. This could happen when you turn 18, or when you move out, when you get your first job, when you go to college, or even when you just decide to stand up and claim your freedom.
When this happens is different for everyone. For me, it started when I graduated high school. Then I felt freer and freer as I got my first car, moved out, started college, etc. I am now in a stage of still trying to stand up and say to their faces, "I am not a girl, I will not be called a girl, and I will not respond to any more requests to be ladylike!"
I started this last stage by cutting my hair really short, and it feels amazing.
I have been in a place similar to where you are. I did not have to wear a school uniform, and I am not sure to what degree anti-sexism laws effect dress codes, but you may have a case for being allowed to wear the uniform pants.
My family did not let me see a therapist either - and I have not been able to afford one since. But you may be able to see someone for free. See if the trans issues therapist in your area offers any pro bono or sliding scale services.
It is also possible to see someone without your parents knowing. I don't know your level of freedom to roam, but you may want to check a local public school or youth center for resources. Some places have support groups that may be centered on other issues (suxch as anxiety) but might point out that they are trans-inclusive. So your mom could drop you off at your anxiety support group, but maybe while you are there you can get a chance to talk through your frustrations and your hopes and your gender identity.
Parents can be tricky, especially when they have eyes and ears everywhere you go. If it is not possible for you to explore or express your identity safely at home, it may be worth it to wait, and to survive all of the harmful, embarrassinf, and just plain wrong stuff they make you do.
I haven't shaved my legs since I moved out. I no longer own any skirts. I am still alive after all the forced femininity they put me through. It is possible.
It can lead to more anxiety and depression than you thought you could handle, but you can still survive.
Everyone here has survived something. Everyone here will support your ability to survive.
I believe that you will be okay.
P
I'm still working on "okay" myself, but it keeps getting better and better.