Shopping Cart Shows Different Item Counts on Different Pages

My site is very new. I had a new customer report that she was having trouble adding items to the cart. In my testing I confirmed this. I am selling cut fabric so I use fractional quantities. So, for instance, if I add .5 yard fabric my cart will show that. If I add another product to my cart (another .5 yard) my cart will sometimes show 1 yard and sometimes show .5 yard. It seems to show an accurate count (of 1) if I go to the home page by clicking the top page banner. But, when I leave the home page to go view another product the cart will only show .5 products. If I view my cart there is only 1 product (.5 yard) showing instead of the 2 that I added. If I add a 3rd product (1 yard of another fabric) when I go to the home page my cart shows 2 items (.5+.5+1). When I leave the home page my cart goes back to displaying .5 items. Sometimes the cart will even show that it is empty. NOW, to complicate matters, while I'm writing this I go back to my site and use it to double check what I wrote here and everything is working perfectly! This makes me doubt it is a logic issue with the code. Could this be a database performance problem? Do I need to complain to my hosting company?

A link to your site so we can see the behavior for ourselves would help.

I called my host's support. It appears as though my site is being cached on the server end. My issue has been elevated with my host's support to find out why. Thanks for your reply, though, stevesh.