My truck ran great for 2 months after I put an external voltage regulator on, but recently it’s been having trouble starting. I’ll go to start it and the dash lights will turn off the cab lights shut off I have no power, if I go and wiggle the negative terminal I get power back and it turns on with no issue. Could it be a loose ground? I can’t figure it out

 

Sounds like a loose ground cable. Check both ends of the cable to ensure it's connected well.

 

Also if I hit bumps/potholes in the road going decently fast my Gen light will flicker on and my RPMs will shoot down but the truck immediately saves itself from dying

 

Sounds like a loose ground cable at the battery as you described earlier. Check both ends of the cable to ensure it's connected well.