The thyroid is under control. you need to continue same dose of thyroid medication. But you should be happy that you are able to lose weight after efforts like diet and exercise. Please understand that once you lose weight, you need to continue both diet and exercise to maintain that weight for a little longer time so that it remains for many months and your body gets used to low calorie diets and controls cravings for food.
Check for vit B12 level for giddiness. Low Vit B12 levels are associated with hypothyroidism
and tend to make you feel giddy. Let me know the report. Take care.