Would you stay with your husband if he became an addict and had been of and on for the last year?

My husband has become a functional meth addict. He works but continue to hang around the people that expose him to it. Childhood friends that he hasn’t seen in over 13 years. It’s like he has put these people and drug before his family. We’ve been together 19 years. He’s tried quitting a few times and can’t handle the withdrawal. During one period of time when he stopped we became pregnant after trying to conceive. Now, I’m pregnant and I noticed last week his behave back to how it is when he uses. I’m just lost because all I can think of is “why?”.

Please someone give me some suggestions or advice.