HPOP seal, oil filter loose or has failed, also the copper o-ring on the drain plug can fail, mine developed a pretty good leak, not as fast as yours but a pretty good spot on the garage floor. I checked the drain plug and it was tight, went to change the oil and the copper 0-ring was still there but would not seal, changed it and all good.
Chris & Dianne
Jayco Designer 3110 SOLD 6-11-2016, looking for the next one.
F250 PSD 4x4 Crew Cab