My boobs have doubled their size and they are so full!! No sign of any leakage though!

Lol, they are getting ready for the milk factory to be in full swing! That's a good sign!

Press on your breast all around and if it's really hard, then it's your milk supply. Feel around your nipple too, if you feel little balls, those are milk ducts

how can you tell ? @kylamommy2016

Could be your milk supply has came in.