It is counterintuituve, but leaving the house to exercise will ultimately increase your energy so you have to keep the end goal in mind.

If your underactive thyroid isn't corrected with medication, you need to address this. You need to get thyroid labs done every six months to be sure your dose is correct.

It sounds like you are on the right track. Maybe you could keep a log/journal of your runs and list what you are accomplishing each time you go out. Consider asking someone to support you and give you encouragement ... something like a 'mentor'.

Best wishes - I know several people who have completed the Couch to 5K program and felt so good about themselves afterward.