Before diagnosis I also put on a bit of weight. I had been 8 1/2 stone for years, and gradually crept up to about
nine and a half. That might not sound a big weight gain, by the wierd thing was I was hardly eating anything, and never hungry apart from getting cravings for fat and sugar. I found that things like coke helped my headaches and fatigue (probably the sugar and/or caffeine), and relied upon sugar to get me through the day. Now, since treatment, I have lost that weight again, and have a healthy full appetite - I eat far far more than before, but don't put on weight any more. I think my low body temperature (and therefore probable low metabolism) was part of the problem.
Hang on in there and things will no doubt get better!