I'm finally starting to put some more miles on the bike, but my butt and lower back is really not liking it. The main pain seems to be in the sits bones (or that general area) and my lower back/butt muscles seize up after a while. After my 20mile rides, it takes me a few minutes before I can walk normally again when I get off the bike. I'm guessing I might need to try a different saddle, but have no idea even where to start looking. My LBS does not have much of a selection in stock and I really can't afford much at the moment. Especially when I don't even know what I'm looking for. Does anybody have any suggestions?

The other problem I have is that I seem to slide forward on the saddle as I'm riding. I have absolutely no core strength and start to slump when I get going. Could anybody help explain what is the correct position/form on the bike? It is a bit frustrating being a new rider with no knowledge and not have any club or coach to ask in person.

But aside from the discomfort, I am really enjoying my 20mile rides. I take the train to work every morning and then cycle half way home after work (my office is 40 miles from my house). It is a beautiful ride through the countryside and it's been great watching spring progress into summer. I just noticed yesterday, a sign by the side of the road has disappeared since last week. The vegetation has grown that much! And what seemed like a very long ride the first time, now seems quite quick and if I can just get more comfortable on the bike I would like to keep going to the next station and eventually cycle all 40 miles home.