I'm a 5th year senior at my university. However, I have only used the American Opportunity Tax Credit once during my time in college. Would I still be eligible for it now?

[HelenaC]

If you have finished the first four years of higher education at the beginning of the tax year, you cannot claim the American Opportunity Tax Credit (AOTC), even if you did not earn a degree. 

If you (or who ever was claiming you as a dependent) did not claim the AOTC in prior years and you were eligible for the credit, you may be able to amend your income tax return. How to Amend (Change or Correct) a Return You Already Filed

Per IRS: https://www.irs.gov/individuals/aotc To be eligible for AOTC, the student must:

• Be pursuing a degree or other recognized education credential
• Be enrolled at least half time for at least one academic period* beginning in the tax year
• Not have finished the first four years of higher education at the beginning of the tax year
• Not have claimed the AOTC or the former Hope credit for more than four tax years
• Not have a felony drug conviction at the end of the tax year

Related information: https://ttlc.intuit.com/questions/3054212-completion-of-postsecondary-college