Parent with addiction?You opinion please?

Ok to start off I am not a child….I’m an adult. I need you opinion on how to handle this situation. One of my parents has been battling a drug addiction for over 10yrs. now. I have seen the ups and downs they have been through. Until about a month ago my father seemed to be doing well, working and paying bills and living somewhat normal, and supposedly drug free. I recently found out that he has lost his job, and started back using his drug of choice ( Crystal Meth ) . However he hasn’t called me or told me this, I found out by someone else. Do I get me self involved or just let him hit the bottom again? I have been down this road before with him, and the only person that seems to really get hurt is me. He can easily brush his shoulders off and show no emotion, but hence that is the side effect of drug use. Should I get myself involved. BTW my husband cant stand my father, so its very hard to discuss this matter with my hubby. (My husband sees the heartache my father puts me through)
I understand that he is my father and I should want to help him…thats not my question… How do you help someone that doesn’t want to help themself?
lillo….thanks for the answer, but yes my father denied me the first ten years of my life. So yes he did turn his back on me.