Yes you're overdoing it. If you're not careful you'll burn out after a couple of months and never ride again. I have seen it happen, LOTS.

Cut back to say 2 or 3 rides a week and concentrate on extending your distance, let your body recover in between. Get a cheap computer and keep a log book of your efforts if you want, that helps in monitoring your progress. It's easy to start cycling but if you don't want to end up obese again in a couple of years you need to make it lifestyle, not a boot camp. And don't forget to oil the chain.

Hang in there