My story is not dissimilar to yours. It seems my husband has lied a lot over the last few years, mainly about small things, but lies nonetheless. His behavior changed around July of last year and I knew something was not right with him. Just like your husband, after being confronted over and over again, he admitted he started smoking again, after years of not smoking. I was angry at him for started smoking again and for lying to me about it, but on the other hand I was relieved as I thought this explained his weird behavior. Fast forward to November of last year and I found out that actually he been having an affair.
We are trying to work it out, but who knows whether we will manage to. One thing he has said to me is the fact that he was a habitual liar, was partly what made the affair possible. He knew he could look me in the eye and lie to me, because he was so practiced at it.
He is having counseling at the moment and facing his lying is something he's having to deal with. it is not easy, because when you've been a liar for years like he has, lies can come out his mouth without him even thinking about it. It's difficult. But I would recommend that if you guys do try to stay together he needs to look at his lying. among other things, obviously.
Like you I'm just taking it one day at a time, I'm not promising anything, but I don't want to make any rash decisions either. Take things at your pace and take care of yourself. Only you can decide what you want going forward. I completely understand the position you're in right now I want to send you a virtual hug. It is hard :(