Congratulations !!
Cycling is addictive and I'll be the first one to admit that. Two years ago, I was overweight, out of shape and gaining weight at an alarming rate.
I started with a hybrid that I bought couple of years before, went out for a ride and came back feeling like something the cat dragged in after 5 miles. I kept on going and after a few months I really , really wanted to get back on a road bike.
Since I was a roadie once upon a time ago, I spent the winter doing my research and got the bike that fit me to a tee, was just right for my needs and I was back on the road in the spring. I also got a Garmin Forerunner that I also use for kayaking (a new sport for me) and xc-skiing (another pastime I've started doing again) as a concession to my wife (not overdoing it and dropping dead somewhere) and for me it was probably one of the best things I've ever spent money on.
It's been just over 6 months and almost 1500 miles later and I've been putting in over 100 miles a week without blinking.
Most of my rides during the week are limited to about an hour because of work and I try to get in about 50-60 miles on the weekends when I have the time.
I've gone down from 192 to 175, my HR had dropped about 10 beats or more and I'm getting stronger and stronger every month. I'd like to take off another 10 pounds but losing the last 5 took me about 5 months so it's going to take a bit. I need to take my bike in and get the stem flipped and the bars lowered down some more so that I can get into a more aero position (speed is addictive as well

).
Take your time, listen to your body and remember not to over do it. Those days off the bike can be just as important as those days off. More importantly, don't forget to eat and drink as well and if you have any questions, don't hesitate to ask.
And don't forget that this isn't just exercise, it's fun.