Hi i have several brown patches on the crease of my arm on the inside where my elbow is and a big one that goes from one side of my neck around the front all the way to the otherside of my neck, it started on the neck with my first pregnancy then went away, it came back with my second pregnancy and seemed to stay, my skin clears during winter but i break out during the summer and when i get hot the patches itch , i also had gestational diabetes with my second pregnancy, what could it be?