What Causes Blisters On Buttocks, Vagina, Thighs And Stomach?

I am 23 years old. I have been suffering from recurring blistering on my anal area since I was 15. It is getting worse. I used to get 1 at a time every now and then. Now I usually have 3 at one time all of the time. I don't just get them on my butt anymore either I get them in my vagina thighs and belly. They are usually 2 centimeters long, wide, and risen 2 cm high. The blisters are full of blood, clears liquid, and light yellow pus. They are very very painful.. They normally pop and drain after a week or so.. When they heal, they ljnnff horrible scars and hard knots beneath the scarring... Please please tell me what this is and how to treat it. I have been tested for stds... I do not have any stds. I cannot consult a dermatologist because I do not have health insurance. I have asked my gynecologists and my obgyns in the past and they did not know what it was... Please help me