Continues Oil Leak

[Where's my car?]

So its been about three weeks now since i've first noticed an oil leak. After getting under the car, i realized that it was my oil filter cap that was loose, so i tightened it.
Just two days later, there was some leakage again.

Throughout the next two weeks i tried to tighten it each time, only to find it leaking again. I finally took the whole filter cap off, cleaned it along with the filter, and refitted it back on. I made it as tight as my hands could possible tighten it. Any clue what i might being doing wrong? Is it not tight enough?. When i pulled off the cap in the first place, it was filled with oil, just wondering if that was normal. THanks!!