I have been with my boyfriend for over two years and I love him to pieces. With my weight, I am very insecure and kept feeling like the more weight I lost the better I would feel.
One thing that my insecurity causes, which is oposite than most, is a higher sex drive. I know that sounds crazy, but in my head, if we have sex then maybe I won't need to worry about other girls because he is happy with all aspects of the relationship.
I've been losing weight since January and I really thought that by now, I'd feel more confident and could back off a bit, but I'm not. I still feel like sex should be a main focus in the relationship.
My biggest issue, however, is that he's kinda sex'd out. He said that we have sex a lot more than other couples and now he's starting to reject me when I'm attempting to get things started. It's making me feel horrible and worse than I did before.
I'm unhappy with myself and just don't know what to do. I'm kind of at a loss. Now I feel like the pressure to have sex is creating issues which is opposite of what I ever intended.
I just feel horrible...

I hope someone else chimes in with some helpful thoughts for you!
Sex is a part of a healthy relationship but after a little while, it does wain a bit. That is quite normal. Don't assume he isn't interested in you anymore or cheating. That likely isn't it. Sexual desire peters off a bit after a while (for both men and women) for different reasons -- stress, fatigue, hormones, pregnancy, time, etc. 