I have two red circular bumps on the back of my left thigh near my buttocks - they are on top of each other. i don't have bumps anywhere else.

Hard to say: Difficult to say without seeing the rash. Reaction to an insect bite is often a cause. If you live in an area endemic for Lyme disease and have been around low lying shrubs or tall grass Lyme disease is a possibility. Various other causes are also possible. If concerned you can have an online consultation at Health Tap. You would upload several images, including close ups in good focus.