Relax. It's not fraud unless you were intentionally cheating. The IRS is not going to come after you.
Someone paying you to take ONE survey would not be self-employment. But when you do it repeatedly it becomes a side business. If you had gotten a 1099-MISC, the IRS would definitely consider it self-employment. The fact that you did not earn $600 from any one company doesn't change the character of activity. I disagree with TurboTaxEliot's answer because the person he was responding to was doing it regularly every month. That's a business activity, not an isolated survey.
I think you should amend your return to report it as self-employment income. That means you will have to pay self-employment tax on it. By reporting it as other income you already paid the income tax on it. To go back to your original question, other income is not counted as earned income for the Earned Income Credit, but self-employment income IS counted as earned income for the EIC.
And don't worry about going to jail. That's not going to happen.
