Reddit mentions of Just Ride: A Radically Practical Guide to Riding Your Bike

Get the book Just Ride from your library as it discusses the equipment needed for using a bike to commute. It also has a lot great information for someone new to commuting by bike. It will help keep your budget under control and keep you from getting a wanna be racer bike that wont last.

Yeah, I had the same problem when I bought mine. It hurt my back to ride it. I think this is one of the places that racing culture has influenced recreational and utilitarian riding. The forward position is to cut wind and get a full extension of the leg when peddling to fully maximize your speed potential...Which just doesn't matter when you're not a racer.

I fixed my bike by swapping out the short downward angle quill stem with a taller, more upright angle, bought fixie bmx style riser bars that slightly slope backwards and a wider, padded seat. I'm not the fastest rider on the road, but I'm not the slowest either. It doesn't take me any longer to get to work now than it did with the racing style setup and it's a much, much comfier ride. More importantly, I can spend way more time in the saddle, which makes me a stronger, better rider since I'm not in constant pain from the bike beating me up.

This book is what tuned me into racing's impact on cycling as a sport. It's a good read:
https://www.amazon.com/gp/product/B0074QGFES/ref=ppx_yo_dt_b_d_asin_title_o09?ie=UTF8&psc=1

I'd recommend you to read "Just Ride" by Grant Petersen. Full of (slightly controversial) wisdom, among other, a lot of it about "racer" traits implied to the rest of us cyclists. Weight craze being one of them.