Is my snowboard to big for me ?

Yeah, it's too long for your weight. The business about boards coming to your chin is crap. It's just what the guys at rental shops do to speed up the process. Boards are generally sized by weight, and a 155 is more suited for someone who weighs 150 lbs to 175 lbs. You can ride it, but you'll struggle to turn it. You'll probably be much more comfortable on a board in the 140-145 range.