I have coccygeal pain when i sit down. i've been having constipation on and off. no bruises or hx of trauma. what could it be and what to do?

Coccygeal pain : my sympathies ! It's painful. Treat constipation. Use doughnut pillow to sit. Treat any hemorrhoids. Do sitz bath with warm water. Give it rest. See your physician.

Use a cushion: You have a painful tailbone. This is a common condition. The treatment is to avoid direct pressure on your tailbone. Horseshoe-shaped cushions are the best. Don't sit on hard surfaces. If pain does not go away, then see an orthopedic surgeon.