Engine not heating up

I have had this truck coming up on two years. Since I bought it, I have had to do a heater core (not fun with freezing fingers), and a thermostat twice. But when the weather is cooler outside (even sixty degrees), the truck does not warm up past around 150. The thermostat is fairly new. The hoses feel slightly warm to the touch, and there is very little heat coming out of the vents. I am not getting any check engine codes. I would think that the twenty five minute commute (mostly fifty five mph and above) would get the heat going. Last winter I let the truck idle for fifteen minutes to warm up, temperature gauge barely rose off the bottom end, and no heat. I needed an ice pick to get through it. I do not want my kids to get sick from lack of heat this winter. Please help! Oh, and the mileage I input as the approximate mileage is exactly what the odometer says.