I can't register for Instagram?

[Emily]

How many instagram accounts have you created on the devices?
The problem is not the email that you are using, but the number of accounts that have been created using your devices (the limit is probably around 3). So, unfortunately your device will not let you create any more. What you could do is use a friends device to create an account on, or use your pc instead to create an account, then sign into it on your iPad/ipod. Or try creating it through safari on your devices.
If you haven't created many accounts on your devices, you can still try the suggestion above.
Good luck, I hope I helped!