BMR and TDEE with hypothyroidism

MelxH

Hello
I was diagnosed with hypo when I was 11, now my doctor says that my thyroid looks ok and in a good balance...
I need to lose around 28 lbs to get into the "healthy" zone, and I've been exercising 5 days a week for 4 weeks with no visible results.
I guess that the problem is that I eat between 1200 to 1400 calories a day, and everybody says that you should calculate your TDEE and BMR and go with what it says... wich means that I should eat 1500-1600 calories... but... I'm pretty scared! I really don't want to gaing more weight, and I dont know if those 1500-1600 calories would be less if those calculators had and option of "yeah.. uhm... I'm hypo" lol
so... should I go with it even with hypo?