I'm not sure if you are cancelling for lack of use or medical reasons based on your question, but if lack of use is the real motivation (along with lack of results) my first suggestion would be to contact your local Anytime Fitness and see a personal trainer to help you get back on track. We all have times in our lives when we think other things are more important (than our health), but ultimately it is up to each and every one of us to look after ourselves. This includes healthy eating and living and regular exercise and Anytime Fitness can certainly provide that in a friendly and warm atmosphere.
As always, different gyms have different policies on cancellations and likewise different states have different laws so I don’t know what they are in your local area, but your first course of action is to contact the club at which your membership belongs to (your 'home' club). If you simply want your membership to stop in Dec (if that is when it is up), you can simply call the 'home' club and tell them you do not wish for it to renew.
I hope we can get you back into your fitness routine and I know your gym will be sorry to see you go.