Sensitive pics, but please help.... :(

So about a month and a half ago, I had a really bad day “down there.” It was the end of my period, I was for some reason extremely wet and sweaty down there, and my jeans & underwear were rubbing on the sides of my legs. When I got home, I had the WORST chub rub I’ve ever seen in m my life. There were two huge bumps, swollen, super painful on the insides of my thighs. Ever since then, the itching has never gone away. I’ve tried hydrocortisone cream, and it only relieves the itching for a short amount of time and my gyno said it just looks like a rash. I don’t know what to do, but it’s super embarrassing and discoloring my skin down there as well. Has this happened to anyone before? My actual vaginal area doesn’t itch, just the inner parts of my thighs. It’s also weird to me that I now have slightly the same rashes under my armpit, on my waistline, and under my boobs where my bra rests. It especially flares up after a workout. If this is something along the lines or jock itch, is this stuff contagious to other parts of the body? Idk if I have some weird STD or something that makes me breakout. I just really need help. See attached pics.

Under boob

Armpit crease, also discoloring because of rash.

Waistline where my leggings sit

Inner thigh