Cylinder is filling up with fuel!

Truck won't start at all, what do you think is wrong? I'm pulling my hair out please help. My 2004 Cadillac EXT check engine light came on and it started running rough and burning excessive gas. I had a tuneup done ur it was still misfiring, with a coil #7 that was changed still came back with misfire changed injector, still misfire wire was changed and code cleared truck was driving normal.

Truck was parked and not driven for 3 days at which time check engine light came back on drove for 10 mins parked on way home truck became hesitant and very shaky parked tried to start car 10 mi s later and it wouldn't start.

Next morning mechanic came and truck started but I heard a low noise coming from truck when he started to pull off only in drive thou. Truck was parked and worked on 2 days later and he couldn't get truck started, he replaced starter! Truck still won't start, spark plug was removed and the cylinder is filling up with gas without the truck running! Please help me with what you believe the problem is I cant afford to keep buying different parts and the real issue isn't being resolved! What is wrong with my only means? Please help!