2005 Dodge Ram oil in coolant

Hi I just bought a 2005 dodge ram 1500 4x4 crew cab 2 days after buying it it overheated so I check the coolant reservoir and it was full of oil but the oil dip stick said full so I took it to jiffy lube and they did a coolant flush know its been 4 days and there is a little oil still in the coolant reservoir it stopped overheating and I checked the heads for leaks or cracks but nothing please help me please