How many PSI are you pushing it at? It sounds to me like your CO2 is coming out of solution. Worst case scenario, take it off the co2, bleed the co2 off the keg, and let it sit for a week or so, then start your process over again.
If you want to force carbonate your beer, 10-12 psi for 5 days should do it, or crank it up to 35-40, shake the keg a few times during the course of the day, and it will be ready to go in 1 1/2 days. Be sure to then drop it back down to 8-10 for serving purposes.
A little more info, might help to solve the problem. A few weeks at how many PSI?
Cheers!