Roller Coaster Weight Loss...How Frustrating

I am getting SO frustrated. I lost five pounds about a week ago but when I got back on the scale yesterday, I had gained back 3.6 of it! What is going on? I know everybody fluctuates but this is getting so frustrating when I am trying to lose weight and the first five pounds that I lose comes back!

I wanted to be thinner when I got back on a horse this year. I cringe at pictures taken of me riding and I didn't want that again this year (not to mention it is bathing suit season which I will NOT be participating in this year).

I am seriously getting upset over this. I didn't want to use weight loss pills but I am thinking about asking my doctor for a little help. I don't have to be a size two again (and I honestly don't want to be that skinny again at my height). I just want to feel good about myself. These are the times that I really hate my thyroid and what it has done to my metabolism. Having an auto-immune disorder seems like such a betrayal of my body.