What Causes Swelling And Itching On Vulva?

I am experiencing swelling of the vulva. There is also redness and what looks like irritation with occasional mild itching, and dryness. (When I first began to notice the symptoms there was stinging and itching.) There is no odor and no burning. There is, however, black skin around the vaginal opening on each side, which I think this is normal (is this correct?). There is also what feels like a large cyst on the right side of my labia and also one on the left which isn't as large. I had to take a large dose of Amoxcycillian about a month ago to premedicate before going to the dentist. About a week ago after these symptoms began I got what I think was thrush in my mouth. I took three Diflucan pills and that problem went away so I assumed this problem was a yeast infection as well. I also used the Monistat 1 day treatment and this did not make it any better. I do have a coticosteroid cream that I've been using and that helps the inflammation. I've only been using that for about 4 days. I thought I might be having a reaction to something. I had put one of those Clorox tablets in my toilet tank. I took this out about a week ago. Would I still be irritated? Any idea what this might be?