Hang in there! Do other healthy things. It'll help with any urges you may have, and any /perceived/ weight concerns. You have a lot of people rooting for you! Congrats!

Be a good idea to get some labs done- while it's most likely that it's just your appetite returning, sudden weight gain can be a symptom of other health issues.

Don't buy new clothes and accept the weight gain. once you do that it's even harder to go back. as a smoker you're already the type of person prone to habit so make exercise a habit. smoking or eating junk food is your brain craving a pleasure reward. you don't need to work out for hours a day you could make yourself do 20 jumping jacks or squats every time you crave a cigarette or extra food. the endorphins released from that little bit of exercise will temporarily satisfy the craving.

Could have been a good reason not to start in the first place? Keep at it OP.