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.