Hello 'lightspeed...',
<<...Is it possible to register another email address with my ebay account but not delete the one i use now,>>
An ebay account is attached to a single email address. If you wish to change your email address on your ebay account, click the My eBay at the top of the page, then choose the Account tab.
From the left side of the page click on Personal Information, and where it says Email and Contact Information you will see Registered email address. You only get to use one.
If you wish to change it, use the Edit link waaay over on the right.
Remember to Save any changes.
It's not really that much of a nuisance.
You should, however, be able to change it back to the one you use now if ever you decide to. For now, though, if you have an alternate email address, it might be a good idea to switch as a precaution.
And of course, change you password on your email account if you have not already done so. Change your password on your ebay account as well, preferably different passwords for the email and ebay.
Always log out of your email and ebay accounts when you are done, and do not share accounts and/or passwords with anyone, ever.
