I've just got back into road cycling, and at 44 a wee bit older than you. My advice would be to get back into the saddle and just go out and ride for a bit in order to get some base fitness and strength back. You should see some weight coming off, and you'l know how you'll feel and at what point you can lengthen the rides. I did a 50 miler on Sunday and felt pretty worn out (it was hot too), but then did 25 miles Tuesday evening and felt really fresh and strong so I attacked some hills.
What I would say, is that you should be enjoying it, othewise you'll stop again. Make sure your bike is working well and not working against you. Get your riding position adjusted if necessary as you've put on some weight and therefore might not find your old position as comfortable.
