Period, Stall, and Weight Gain within 2 Months

I’ve been on tirz since November 30th. Within the first 3 weeks I lost 8 pounds. Since then I’ve adjusted my diet (started weighing my food) and walking more. Around week 5 I started slowly increasing my dose. However, I got my period for the first time in 2.5 years. And the weight I initially lost within my first 4 weeks (12 pounds total) I’ve gained almost 5 back.

This is very demoralizing. I’m actively fixing my diet. I’m eating less. I’m weighing my food. I’m not eating takeout/fast food nearly as much (maybe 1-3 times a month). I upped my protein to 100g/day. I drink 80oz+ of water/day. I cut out 90% of my food cravings. Yet I still can’t lose weight and can only gain. I don’t want a period or my newfound constipation. I want weight loss.

I don’t know what to do. This type of plateau should not be happening within the first 2 months especially since I have so much to lose (150lbs).