Will I be able to exercise without muscle pain?

Exercise would certainly help as far as hypothyroidism, hypertension and fibromyalgia are concerned. Be gradual in increasing your exercise routine since you have a sedentary lifestyle. You may find increase in muscle aches for the initial few days but it is important to be slow and steady. You cannot expect to exercise the way other people in the gym are doing from the onset. Do not be disheartened. It is important to note the following:

1. Exercise under the supervision of a trainer who knows his job well.
2. Optimize your medication and diet with your physician. Ensure proper calcium intake. Restrict extra salt intake.
3. Be patient.