My compression garment causes a severe back ache and abdominal pain while lying down. Is it ok if I only wear it during the day?

This is a question you should ask your surgeon. I generally advise patients to wear their garment for at least 3 weeks after surgery, day and night. You may find that wearing a thin shirt with no seams underneath your garment helps with your rash (which could be an allergic reaction to the garment). However, your garment should not cause you a severe back ache and abdominal pain. This may be because it's not fitted properly.