Overheating and misfiring

So today while I was going to work I noticed the truck was misfiring so I pulled over checked the oil and it wasnt even registering on the dipstick, 3 quarts later the oil was good but it was still misfiring so I figured it was a bad coil and decided I would deal with it after work. Then about 5 miles down the road it started overheating so I pulled over again and the radiator was out of water so I filled that up. I made it to work but on the way back, it did it again so I pulled over and the radiator was dry again so then I started thinking head gasket, so I checked the oil but it was fine, not low good color and good consistency (not milky) but when I opened up the oil fill cap there was a thick milky residue on cap. So ime kind of thinking head gasket but I dont see why all the oil wasnt milky. Anyone have any thoughts? Thanks in advance! Oh yeah when I ran the codes it was a multiple misfire