Gaining weight..

I've recently gained a lot of weight, I'm 212lbs and I used to be 160 a couple years ago and I looked good, I drink a ton of water, don't eat a ton, and walo a lot because it's my main form of transportation, my fiance is losing weight and he drinks pop and eats a lot but I'm gaining and I drink water?? I've had my thyroid checked, it's not that. I had it checked a few days ago and it depressed me so much I barely ate anything the next day and I cried whenever I thought about it. My fiance thinks I'm about 170 but I won't tell him my actual weight.