bad gas mileage, idles rough, check engine flashes if you press the gas pedal too hard and sometimes you can smell exhaust fumes but not always
So the check engine light is ON all the time??
The list of possible problems is endless. The check engine light is telling you to get the truck serviced, soon. The blinking CEL is telling you to stop driving the truck before really bad things happen and service it NOW.
You keep driving like this, you need to be shopping for a new truck, you are destroying this one in only 6 short years.