Hi topher76, welcome to the forum! First make sure in the receiver tab of your flight controller gui (probably cleanflight) that the yaw, roll and pitch have a midpoint as close to 1500 as possible. Values off from 1500 will cause drift. Second, as TexasTeacher says, if you are flying in autolevel/angle mode, make sure you calibrate the accelerometer on a flat, level surface. Try your best, if it is slightly off you can trim the accelerometer. I'm not sure how to do it, but you can probably easily look it up. Finally you may need to tune your PIDs. A low I gain can cause drift. Make sure you try to get it level in acro mode first because adding on autolevel will only add another layer of factors to cause drift.