Steam out the tail pipe

My truck is in real good condition. I baby the vehicle. I have noticed that even after I do a lot of driving the steam does not ever burn off it continues to blow out a little steam the whole time the truck is running. It doesn't run rough and it is not much steam. Basically just like when you start it on a muggy day the problem is it never goes away even after the engine is warm. It has been going on for about a year. I have checked to make sure it is steam and not smoke. I also checked to see if I was losing antifreeze/coolant and I can only check the reservoir and it appears to be not losing any. I am stumped. I recently replaced my EGR valve and that did not fix it. The truck seems to be running fine. I change my oil regularly the only thing is it has been about 4-5 years since the coolant was changed. I know it is time. I was thinking it might be a leak in the TPS sensor or a small leak in the head gasket could you drive 1 year with a small leak in the head gasket? Is it possible if the TPS sensor could possibly leaking? I don't know. I know the TPS sensor regulates idle air, but I thought it has a passageway for coolant too. I'm probably wrong, but could you clarify?