Hi KTeach
I'm sure you're not really a fat slug. Slugs don't have legs so how could they ride a bike
Why not try reminding yourself what it was you liked about riding in the first place - you know, real basic stuff like the feeling of the breeze in your hair or that all-over good feeling you get when you arrive home after a long ride, tired, with aching legs but satisifed and (for me) kinda proud I went out there and did it.
I'm sure you must have a favourite ride. Why not just go out and ride it - simple as that. But really take your time and enjoy it. Don't take any heart rate monitors or mileometers, just ride, enjoy the scenery, enjoy what it feels like to be on your bike and don't worry that you've been off for several months.
As difficult as it may be, try not to compare your performance to that of a few months ago, just be kind to yourself. This is now, this is where it starts... just go out there and give it a try.