This is a member to member board, so no one can check your account for you.
I would suggest that you close down your computer entirely and let it rest for a half hour or so. When you come back the problem will probably have resolved itself.
If you are buying from two different sellers, you will not be able to combine the shipments.
If you are buying from one seller who lists on two eBay sites (like dotCOM and dotCA) he will not be able to combine the payments. This happens more often than you might think.
If your US seller is using the Global Shipping Program,he will not be able to combine your payments or give you a shipping discount.
Hope this is useful!
