Oil on spark plugs?

I had put on about 8,000 miles and I got a misfire in cylinder 3. So, I changed all the spark plugs and the coil pack for that cylinder. Then about a month or two later I had another misfire, but in cylinder 1. So, I changed only that plug and coil pack. Then a few days later I was driving my oil light flashed and then my truck shut off, but also when I changed the spark plug for cylinder 1 there was oil on it, however my oil level has not dropped at all just the pressure that one time. I do feel it being sluggish and not as peppy as it was.