How do you stay in a marriage with a compulsive liar?

[sew lawst itz knot fun-e]

For 4 years now I've been lied to about every imaginable thing, from 'Did you pay that bill'?, to 'Where'd that pint in your pocket come from'?. I have a 9 year old son who sees and hears this lying as well...what are the consequences for him to bear witness to this awful behavior by one of his role models? Certainly I'm hurt and angry and there seems no end in sight for this behavior that time and time again I've been told 'I won't do it anymore, I promise', but is there hope?I unconditionally love them, but this really taps my resources for emotions, I'm lost.
I'd like to add some things so that I can maybe get even deeper advice, you all are excellent!
Details like:
-he is willing to seek therapy and admits he lies compulsively
-before I was married I was a single mom
-yes that's right, my son is not his by blood
-no, I do not want my son seeing and hearing this, he is first in my life
-my son is aware of my husbands lying issue and understands that it is wrong
-I am a stay at home homeschooling mom
-I have no car and no financial back up (yet)
-and nope, I don't fly off the handle when the truth is finally told, I'm more likely to go off the deep end when I've been lied too

I know I don't deserve this, I've always been strong emotionally with little leeway for unacceptable behavior, however I did marry him (without knowing his habit).
Does it show my son that working out a problem is better than running or just duck out while I am still sane?

[KMK28]

I couldn't stay... But maybe some sort of therapy could help his "sickness"

[butterfly]

You deserve better, put yourself and your son before anyone. Good luck.

[BabeHeart]

Get this person into counseling or the behavior will never change.

I would not marry someone with that problem, if I knew it existed beforehand. Trust is part of a relationship foundation and there can be no trust when there are lies.

I don't believe in unconditional love outside of parent/child. There are a number of conditions for my love...as there should be. I think it foolish to love someone who would lie to you, cheat on you, steal from you, abuse you, or otherwise harm you or your loved ones. I don't feel bad at all not loving such a person. They don't deserve my love.