Yes you may.  You might still qualify for the American Opportunity Credit if you have not taken (or your parents have not taken) 4 years of the credit on you yet.  You may also claim the credit if you graduated in June and started grad school in the fall.  You may claim the credit as long as you were an undergraduate at the beginning of the year and had at least 5 months of school.  

Again, the key is that you have not had the credit claimed for 4 years previously, either by yourself or your parents in your behalf.  But even if you no longer qualify for the American Opportunity Credit, you may still qualify for the Lifetime Learning Credit.  So you may want to fill out the Education section to see if you qualify for either of these credits.  This FAQ has more information:  https://ttlc.intuit.com/replies/3301953