Withdrawal effect on Aid

So right now, my tution is fully covered by maximum pell grant, and Comet Transfer Scholarship, and undergrad education grant. I take MicroBio at Collin College, and Orgo2, Genetics, and A&P at UTD, and I got about 3k in aid refunds this semester. Now I am not getting a degree at UTD, I am just finishing prereqs before starting Pharm school next semester. A&P is not a requirement, and Im thinking about withdrawing. But that would drop me to 8 credit hrs instead of 12, since micro is at a different college. Would this affect my aid? Do i need to pay some back if I drop it?