That is going to be close. If you are not flying Delta then you will most likely make it, since in that case the airline is likely in one terminal with fairly close gates. If you are flying Delta you may not make it depending on which terminal you land in and which terminal you depart from. If I was you I'd see if it is possible to get the flight changed to give more time for the layover. Since they have changed your flight twice already they should be willing to change it again for no fee (though no guarentees). Having spent years in Atlanta and using the airport, I wouldn't want to be a on flight there with only a 38 minute layover, especially when most planes start pre-boarding 30 minutes before the flight.