Lately I've been noticing that my coolant level inside the radiators been dropping, there is no leak anywhere I've checked, but what I also notice is that while its dropping inside the radiator, it's filling up on the little reservoir that sits out to the side of the radiator, is this a sign of something?

 

does the car smoke? does it run hot?

When the car is running do you get bubbles our the radiator cap?

Like, take off the cap, (when it's cold you idiot! no, seriously, be safe, do it when its cold)
Start the car, let it idle till it gets warm and you start to see coolant flowing through the radiator. Do you get bubbles or smell exhaust fumes coming out the radiator?

How old is your radiator cap? it might be old and worn out. if that happens then the spring can't contain the proper pressure in the cooling system, and will purge sooner than it should (which would cause the coolant to flow into the overflow reservoir.

 

Had this exact same problem. Went through this whole list couldn't find out why. Turns out the mating serface for the cap in the rad was damaged. Everything he said was correct, but I would just try replacing the cap before getting into blown head gasket stuff.