Hi I Need Help On What Is It Or Caused

Hi I need help on what is it or caused this break out on my buttocks. It's a break out of a lot of bumps reddish in color, a little painful and they itch and I do not know what happened or caused this. I am taking some clotrimazole cream for yeast infection and I did have sex the day before, so when I woke up the next day that is when I felt some itching on my buttocks area and felt the bumps.