Veterinary questions? Ask a Vet for Answers ASAP
Without further information it is very difficult for me to provide the best advice but I will certainly try.
Please reply when you can and we can continue the conversation.
An increased thirst is always a big worry and could indicate kidney failure, a urinary tract infection, Cushing's disease or a cancer.
If the weight gain is focused on the abdominal area, this could be due to fluid build up, a bladder stone or a growth.
A vet visit is best so we can have Freddie Winkle examined and the vet may analyse his urine or perform some imaging, so we can determine what is going on here.
I do hope this has helped and please let me know if there is anything else.
Wishing Freddie winkle all the very best.