Paypal help

Omg this is so frustrating! Ok so anyway I'm trying to buy something online with my debit card. I try to pay as a guest, but paypal says I have to sign in because my card is linked to an account or w/e. So I log in with my e-mail, and for some reason it's saying my card is linked to another account. I don't get it. How do I find out which paypal account my card is linked to? This has been bothering me for about a week now, so I just went to the store and bought one of those pre-paid cards to buy what I want, but Paypal is saying it can't verify that card. wtf. Can anyone please help?