So I really want to come out soon the anxiety is killing me but I'm worried if I come out and then decide I'm fine with being male, I have a plan where I'm going to go in town with friends when they go I will stay a bit and buy so things like fake hair, nails a bra etc then either when my parents are out of the house or a night I'm simply going to dress up in it and see but what will how will I know
You will not necessarily know because of that. Do you feel consistently female? Do you experience dysphoria? If the answer to both of these is yes, then you are almost certainly transgender. (Not that dysphoria is necessary, it's just a clear sign.) If you have felt like that for a long while, then your feelings are probably permanent. In terms of crossdressing / dressing for your actual gender, it could just feel right. You could well just know. I would think that it would be unlikely, however. It is best to do some soul searching. Write some tables of things that you do / like that are female, if it helps. That helped me a bit, even though I didn't do many stereotypically female things.
