Unfortunately, the wrong mattress can aggravate the existing pain you already experience with fibromyalgia. A mattress that doesn't provide adequate pressure relief and spine alignment typically spells trouble for your lower back, hips, shoulders, and neck. An overly soft mattress tends to let your body sink in too deeply, putting additional pressure on those sensitive areas. A mattress that's too firm won't provide enough cushioning.
In short, a subpar mattress won't do anything to relieve fibromyalgia-related aches and pains and could even cause additional discomfort.