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!
Sharing my adventures and travels with lyme at http://adventureswithlyme.wordpress.com/