If, as you indicate, you have completed the first four years of post-secondary education, you are correct that you can no longer claim the American Opportunity Tax Credit.
This would still leave you eligible for either the Lifetime
Learning Credit or the Tuition and Fees Deduction, if you meet all other requirements for these.
It may well be true that income is a significant factor in denying either of these benefits to you, as all three of the federal educational tax benefits contain provisions to phase-out the benefit at certain levels of Modified Adjusted Gross Income (MAGI). The phase-outs are different for each benefit.
For specific information, please refer to this IRS
Education Benefits Comparison Chart.
