Blender Crashing while saving

Hey guys, I’m starting to use blender now and everything was working pretty fine until I start Sculpting my character.
I’m working in a very very simple character and I’ve only sculpted the head this far, but I can’t go on because the software became VERY slow, and every time I try to save it simply crashes and closes.

I must be doing something wrong in the software, because I don’t think it’s a problem of my computer’s performance.

Workstation:
OS X
Memory: 16 GB 1600 MHz DDR3
Processor: 2.5 GHz i7
Graphics: NVIDIA GeForce GT 750M 2048 MB

Can someone please help me? D:

I realized that Blender is only using 1,02 gb of my RAM memory!
do any of you know how to change this?
please?