Hi Chris,
I switched over to the pump about a year ago, but back when I was on shots (syringes, never liked the pen), I’d occasionally get problems like you describe. Mine was usually the result of getting lazy and re-using a syringe (gasps of shock and horror from the masses…). I guess I rotated sites enough to avoid building up much scar tissue.
I got pretty good at giving shots on the inner thigh. Plenty of fat in there. I could pinch a good chunk of meat and give the shot there…most times I could hardly feel it.
Hope you get things sorted out. Best wishes and cheers, Mike