Think i may have blown a headgasket, want a second opinion

So my jeep(93 XJ, 4.0 HO, 192,xxx miles) has started running really cold, like just over 100 degrees which led me to do a little inspection of the cooling system. I am pretty sure my thermostat is stuck open, but when i was topping off my overflow after noticing it was low i noticed a lot of sludge in it, so i pulled the radiator cap and same thing, lots of sludge. I put a new radiator in about a year ago, flushed everything clean and replace thermostat then too so i figured something new must be causing problems. So i fired up the jeep with the radiator cap off and sure enough there were bubbles coming up through the radiator, slowly, but at fairly consistent intervals (also little bits of sludge were floating up too). Then i pulled some spark plugs and noticed a large buildup of white stuff on the plugs from cyllinders 2 and 3 which if i am not mistaken would indicate burnt coolant (4 and 5 had almost none of this buildup, and i got too cold to fiddle with 1 and 6 to get them out). I haven't pressure tested the cooling system yet but so far i am pretty convinced its headgasket, there is no coolant in the oil though, or if there is there isn't enough to see with the naked eye so i assume this must be recent. Anyone else have these problems and determine it to be something else? Does it seem like i am correct in determining it to be the HG?

sounds like it.
To be sure, find a place that can do a hydrocarbon test. This will tell you for sure that combustion gases are getting into the cooling system.

With cold engine, remove rad cap - start engine and hold palm of hand over cap hole. Rev engine and if compression is leaking into cooling system, you'll feel air pulsing on your hand. Obviously for safety reasons, only do this with a cold engine.

Still not 100%? Do a leak down - compression test.