It could be a few things. Let me explain what I changed just 4 months ago. You might even find it in the search area. First I had the same problem as you. It turned out to be my rear main seal.... Then it was dripping from not just there but in many other places. So they found it to be the following.

Rear main seal
Torque Converter seal
Valve switch in back of engine top part
And finally, some seal that acts like a cork. ( I can't remember the specific names but I'm sure you can ask and they will know) But once all this was done. No more leaks. My advise to you would be to check all these items. Tell them to pour a dye into the oil and see where the oil is leaking from. Then change what is needed.. GOOD LUCK. I hope this can help you...