No weight gain ever previously. stable at 53k for 1+ years. suddenly, in 2 weeks went from 53 to 56kilos. nothing has changed, diet, sleep, stress. exercise 30min everyday. tsh 2.2 in 12/2013. nervous

Possibilities...: First distinguish fluid weight (like edema, ascites, "third spacing") from tissue weight (e.g. Bodybuilding, reparative, tumors, adipose). There are lots of metabolic reasons to rule out (organ disease like heart, liver, kidneys), insufficiency (thyroid, adrenal, kidney), more. Often high calorie (but low volume) foods ; drink (including alcohol) may add up quicker than you think.

Need to be checked: Thanks for asking as this suggests something is changing in your body. It helps that you have already considered many things that can affect weight. Other things can as well, including some medical problems like thyroid disease, and even heart failure. But likely you would have some other things happening as well, and thyroid disease does not usually cause rapid weight gain. Best to get good exam.