Not sure whether to separate.

Currently living with my fiance, been together for 6 & 1/2 years, and we have a 1 year old son together. I've found nude pics and sex pics of women on his phone, I don't know the woman and he says she's a relatively famous football player. He sends flirty messages to women and says there's nothing flirty about them. It's been happening throughout our whole relationship (yes, more fool me) but now we have a mortgage and a son it's harder to separate. I told him with all the flirting and lying it's really beaten my confidence down and it's like emotional abuse. I'm always unhappy, feel like I've wasted my life with him but obviously I still have love for him after all this time. Don't know whether to stick it out for my son or start the ball rolling and sort my life out?