Std or something else??

Can an obgyn prescribe meds for an std or do you have to go to a health clinic for that? I've been experiencing some itchness down below. Like my vagina gets real irritated and itchy to where I feel like sticking a toothbrush up it and scratching. I'm not sure if I have an Std or what's going on? I'm married and haven't slept with anyone but my anyone else experiencing this??