are you sure the belly thing isn't flab (skin) from losing weight? if it is, time will help. Toning exercises will also help - esp crunches but please be careful of posture... straining neck will not improve or expedite abdominal toning!
you used to enjoy going to the gym. i bet you can pick that up again, but you don't have to go from zero to full throttle. since you're not feeling good, i think the idea of going 3-4 times a week might create too much pressure and feel overwhelming.
what if you made a date with yourself, to go there just once
. see how you feel. then take it a day at a time. maybe make another date... but not on any particular schedule. it might give you some positive feedback - get you back into feeling like going. then picking up your routine again won't feel so hard.
Canceling the membership would not
a failure! but i encourage you to keep the membership, and try to just take things one day at a time.
~ waves ~