How do I make sure that I am eligible for AOC? Not sure if I have claimed before or has reported 4 years

To claim the AOTC or LLC credit,  your MAGI must be below $90,000 ($180,000 for joint filers). You can claim AOTC up to 4 times per student. After that, you can claim LLC unlimited.

You would need to look at prior filed returns to determine if you have claimed the credit. If you have already filed it 4 times, the IRS is quick to send a letter letting you know that you have already claimed it.

Any times that your parents claimed the AOC, while you were their dependent count against your four allowable times.  Form 8863 would have been part of their/your filing if the AOC was claimed previously. In recent years, line 29 of form 1040 would show part of the AOC.