Hi WieWaldi
There's nothing new under the sun!
I'd imagine every possible blues lick (especially in the key of C) on Piano has been done. You're right you are never going to come up with something completely original. i certainly don't. But after a time you will start to feel the blues, and though you may be playing something that's been done before, eventually you won't be doing it knowingly.
Listen to these marvellous recordings of Oscar Peterson:
Notice how he, and the band, stretch and bend the time. Now of course this is incredibly advanced playing (from another universe!) but it's still the blues, and though he's playing some incredibly fast runs, and chordal stuff he's still using that blues scale quite a lot of the time.
Incidentally these are from my favourite Oscar Peterson album "The Trio".
The first 3 tracks are a masterclass in blues playing.
As @rsl12 says just keep trying. One day you'll be playing a blues in the key of C, and it'll stop feeling crap and you'll have made it to first base. Don't be disheartened, it will happen, but you'll have to work at it, and you must get away from copying exactly what's in the sheet music.
And if you manage to do that, it's also a lot more fun!
Cheers
