I had the same problem, too. I gained so much weight without eating so much.
I´ve done some reading and here is what I found out:
I agree with the other poster: It could be your thyroids. Candida supresses the function of the thyroid - too many bacterias. Since I take 1-2 tblsp. of Coconut Oil every day and started again with probiotics my body temperature is normal again, and I lost weight. (The good bacteria from the prob. help the thryoids function again and kills the bad bact. that is surpressing it.)
What I also changed is my activity. Before I felt really weak no energy for sport or such. If this is your case as well take Calcium & Magnesium (Due to Candida your body cannot absorb this from what you´re eating and takes it from the bones - which makes you feel weak) and start working out 3 times a day for 20 min. I am pretty sure this all would help you as well.
The weight you put on is the bad toxins. It is so much, that your body cannot (due to being influenced by Candida) build it down. So the body stores it. You need to sweat it out, drink it out (keep drinking a lot of water) and fill your lungs with a lot of oxygen (even it you just take a walk 3 times a week) to help building it down and killing the Candida.