i went to my doctor and she took a look at the sores that were present between my buttocks, the inside of my thighs, and inside my vaginal canal she said it looks like herpes but ever since i took antibiotics once which was valtrex i haven't had an outbreak and that was 4 months ago. I s it possible that i could be miss diagnosed. Also I was able to donate plasma. Are physicians supposed to test for stds other than AID/HIV?

Just a visual diagnosis for herpes is not enough. The doctor should have taken a swab culture and typed it for herpes 1 and 2. And an IgG blood test. Since she did not and if you don't have any active sores/lesions at the moment, I suggest you go get the type specific IgG blood test (HerpeSelect is most common 'brand name'). STD test do not routinely include a herpes test. You have to specifically ask for it and I'm not sure why your doctor did not do one when you went in to see her. However, you should get tested so you know which type you have IF you have it.
Valtrex is an antiviral medicine not an antibiotic.
If it does turn out to be herpes you are still able to donate blood.