weird rash comes at uncommon times?

[hellieh:D]

Okay so i keep getting a rash at random times all over my body. it is an allergic reaction i am guessing. i first noticed this rash 3 years ago while playing basketball. after my games it would just start forming on my body but it was very settle. the next year during basketball i started to get the rash even worse. it would stay for a couple days and sometimes even a week. and it would form during the games instead of after. after basketball season track started. i began getting the rash during track practices and meets. after track summer started and i went to water world and got the rash. then a month later i went to the hot springs and i got the rash all over and i felt it coming on my face because it burned and my left eye swelled up. i also get the rash when i get nervous. one time i was doing homework and out of no where i got the rash.

i have noticed that it starts along my veins and in places that rub (armpits, thighs)

i had a birthmark through surgery removed 2 months before i got the rash for the first time.

its not a heat rash because i have gotten it at cold track meets.

i went to a doctor for it and they couldn't identify the cause so they told me to take benedryl and it didnt stop the rash.

the rash looks like red dots with white halos around it. some are raised and some aren't.

the rash sometimes burns, itches, or has no feelings.

please post any help. should i go to a dermitoligest ? any ideas whats causing this?