I have some raised circular rashes on my legs and thighs. Can you tell me what is causing it?

Probable fungus. If the rash is raised, reddish on the cicunference and regular skin color in the center, this sounds like "ringworm". Ringworm is not caused by a worm but is a fungal infection called tinea corporis. It is common and treatable with topical antifungals. You can try the creams used for athlete's foot or see a doctor for prescription. One source of the infection is pets. Have them checked.
Nummular Eczema. Nummular eczema is an allergy-related disorder in which itchy, coin-shaped spots or patches appear on the skin. Causes, incidence, and risk factors the cause of nummular eczema is unknown, but there usually is a personal or family history of: allergies asthma atopic dermatitis other possibilities are fungal inections and psoriasis.