Is it safe to drive my truck if its blowing white smoke?

I drive a manual f350, just today i was taking a short trip to do some errands, i was on a ramp to enter a highway only in 3rd gear, i wasn't accelerating or letting off the gas and noticed the idle went down even though i wasn't letting off the gas, so i sped up and eventually shifted to 5th gear. I held the acceleration at 60mph, then noticed it started slowing itself down, and looked in the mirror and noticed white smoke coming from my pipe, when i accelerated it sped up and the white smoke disappeared. I am wondering if it is safe to drive, this just started happening today, and could it possibly be coolant getting through a cracked head gasket or problems with the turbo?