Zoloft and Weight Gain...how long does it take?

Hey everyone! I have a couple questions for you.

I was on Zoloft 50mg for 4 years. I was always around 120-122 which is a healthy weight and I was happy with (I'm 5'3 btw). I reduced the dose to 25mg last year because I thought it was causing thyroid problems. Turns out I just have a thyroid condition unrelated to the Zoloft and it could change over time but right now it's fine and isn't causing any problems. It was checked recently.A month after reducing the dose I lost 8-10 pounds and it stayed that way for months. I was still eating 3 meals a day and everything as normal. The next semester I commuted instead and didn't have classes everyday so I slept more than I ate. I only ate 2 meals most days and I went down to 105/106. However when I was on the 50mg a lot of times I would sleep till 4pm and only eat 2 meals and I never lost weight. I caught some kind of diarrhea virus or either it was a mild case of food poisoning a couple weeks ago and went down to 102.5/103 cause I wasn't eating much. I kept losing weight daily and going down. I looked very emaciated. Stick thin and my face is sunk in. My doctor diagnosed me with anorexia induced by anxiety and had me go back up to the 50mg. She also wants me to start seeing a therapist and she wants to see me again in 4 weeks (about 3 weeks now). I have been taking that for 5 days now and I took 37.5 for 3 days prior to that. I do feel a difference in my anxiety. I'm calmer but I'm not as calm and carefree as I was on the 50mg before. Does it need more time to get in my system? How long does it take? I'm stressing it isn't going to work. Secondly when will I gain the weight back? I haven't lost any more weight which is good. If I had stayed on 25mg I would be below 100 pounds now cause my metabolism is so fast it burns off everything I eat instantly. The Zoloft slows it down. A positive side effect I actually like. But I haven't gained any weight yet. I'm still 103 help!

I forgot to mention this has really taken a toll on my hair too. It's very thin and dry and mats/tangles together. Just awful. I want to color treat it. I've been wanting to for months but I can't

Thanks everyone!