I couldn't find the "XTS 225" on the Giant web page, so I don't know what kind of bike you have... but to me, it sounds like you've got problems with your fit. When I rode my new bike the first time, it killed my lower back. I went in & had a professional fitting & I've been happy ever since. If a professional fitting isn't in your budget, there's a book that I've heard people recommend... Andy Pruitt, maybe?

If you could post a picture of your bike, and even better, a picture of you riding your bike, I'm sure some of the more knowledgeable women here would give you tips for what to adjust. Typically, the LBS will try to get you set up on a bike that is roughly the right size. Then, you often have to make adjustments to the saddle position & to the handlebars.

One other question, is your new bike a different style of bike from the old one? And are the handlebars different?

Don't worry. You'll definitely be able to get it sorted out, and be riding pain free & with your smile on.

Congrats on the new bike!