1995 Pontiac Grand Am Temperature gauge reading low/Overcoo

Hi.I have been working on cars for some years now and I am stumped on this one.First off,my car has a 3100 V6 engine.When driving,my temp gauge never reaches the normal temperature.It stays at or below the first notch(see pic) the whole time I'm driving.If I let the car idle for awhile(atleast 20 or more minutes) it will slightly increase,but never reach normal.I replaced the temp sensor(I got conflicting info on which one was the temperature sensor and which one was the temp switch)near the thermostat housing with no results.I replaced the thermostat with a 180f because these motors blow intakes frequently,but i don't see how 15 degrees would make such a difference.Also,I get warm heat,but not hot at all.I can't see it being the gauge because of the loss of heat.Any help would be greatly appreciated.Thanks.