You're probably at a high ash accumulation. If you don't get it to a shop you will start getting derates, eventually it will shut down to idle speed. Need to get a laptop and technician on it at this point.
Make/model and year of truck and engine? Ditto Mike's question and when was the last time the filters were pulled and cleaned? Take it to a shop with a computer and have them run a forced regen, record the beginning and ending pressures and the temperatures. Check all of your wiring connections. Examine your exhaust system from the manifold where it bolts to the engine and all the way back to your stack. Pull the sensor on the engine and swab the soot out of it.
There is something wrong with the emissions system, so it needs shop time. 350k miles is about the point where you need to have the DPF filter serviced in any case. A 2014? It should still be under warranty.