Camshaft sensor message

My car has been running really rough, jerking back and forth, losing power and cutting out. We took it to O'reilly's and they ran a test and it came back with a camshaft sensor error. So, my friend helped me replace the camshaft sensor. It ran fine for about a week (but would still lose power at around 4000 rpm's) but now it is cutting out and jerking back and forth at any rpm.

Since it said that it was the camshaft sensor, and we replaced that with a brand new one, what else could it be?

Thanks so much.

Erik