First I would like to get a complete history. How old are you? male/female? Since how long have you been suffering from hypothyroidism? What are your recent levels of T3 ,T4, TSH? Are you on Eltroxin? Any other significant medical history?
Hypothyroidism itself can cause very low moods and depression
. Another possibility is that are you nearing your period date. It could be Pre menstrual symptoms. Another possibility is that you are worried or anxious about something.
In the meantime what you can do is listen to good music..instrumental/bhajans/rock anything you like..which you feel will lift your mood. Call your best friend and say you are feeling down.Talking and opening up to somebody you can trust and who understands you , will make you feel better instantly. Watch a movie. Pursue your hobbies. Meanwhile, learn to relax. Join yoga/ meditation
classes. Eat a well balanced meal. Try exercising regularly 5 days a week ( if you dont have any other medical problems).Exercise will be very good for you.Join a gym/ go for aerobics
classes. When one exercises it releases endorphins, which help, as endorphins have mood elevating properties. If you are new to exercise start at your comfort level ( maybe for 10-15 minutes in the beginning and as days progress gradually increase your work out time to 30-45 min per day) . I hope this advice helps. Have a great day .