I started biking more regularly this summer, and at first, my bottom and my shoulders wouldn't let me bike very far because they would soon start screaming in pain. Once I got used to the positioning, I was able to ride further. I'm now able to do 40 miles one day, and then do 30 miles the next. You'll be able to feel the difference as your body starts to get used to being on a bike. As you become more comfortable, you can then start pushing yourself more. But, don't push until you know you can handle it otherwise you won't have much fun and won't want to get back on the bike.

Good luck!
Sheesh