login says my apple ID doesn't exist, and when I try to open an account, it says the apple ID is already in use ???

When I go to icloud.com and try to log in (using my email-address), I get a message saying that apple-ID or password is wrong. If I try "forgot my password" and type in my apple-ID (still using my email-address) it says:

No Apple ID Found.

We can't find an Apple ID matching the information you provided. You may have entered a name that doesn't exactly match our records.Try again

When I go to "create apple-ID" (and I'm still using my email-address) I get the message: This email address is already being used as an Apple ID.

I'd be grateful, if somebody can help me.