Is there a condition in which you can get tendonitis in multiple areas of body, have it in both wrists, left elbow and now maybe in knee. Help?

Fibromyalgia? . 23y female w. IBS & pain "elbow, wrists & knee" considers "tendonitis". Absent injury, & if pain upper & lower back, consider fibromyalgia; highly associated w. IBS. People w. FM have multiple tender points; possibly generated at loci of chronic soft tissue strain & spasm at ligaments, tendons, muscle & fascia. Young females w. FM oft have benign Hypermobility Syndrome; see Brighton criteria.
Fibromyalgia. Diffuse soft tissue tenderness suggests fibromyalgia. You need to see a rheumatologist.