First, check for any wetness around the valve cover, engine bay and underneath. If everything is dry and clean, investigate the other areas above.
Also, make sure you "measure" the oil correctly: level ground, engine warmed up, but off, wait two minutes, check MMI then. Looking at it while driving is not the most accurate. I'm just saying that in case, you looked at the oil level while driving off after the last oil change thinking it was at max. It may not have been.