My husband is a drug addict... advice needed

I knew he had an addictive personality when we met 13 years ago but he was open and honest about it and became clean.

We got married in 2013, and tried for baby right after. It took 5 years to have our miracle child, a sweet baby boy. As soon as I went into labor something seemed off. He wasn’t around. Didn’t stay at the hospital to long. Kept leaving. We got home and he was distant. Didn’t want anything to do with me or our son. It’s been completely heartbreaking.

I’ve caught him in several lies recently. I know when he isn’t acting rational or normal. He flips out when I walk outside and find him in the garage. Quickly dropping whatever he was doing with an attitude like I was spying on him. I saw he made a fake fb page to get in touch with his dealer and have been watching his conversations daily on the fb chat app. He’s admittedly (to his dealer) cashed in our change jug, pawned my watch, and taken from our sons piggy bank for his fix. Apparently his dealer lost his phone and this was the only way to communicate. As of today, he has no idea everything I know and it’s been hard to look him. I need advice on how to approach the situation. Anything would be very helpful. I can’t keep living like this looking for proof, being lied to, having things stolen. Worrying about if he’s driving around with our son while under the influence. But I do realize this is an illness and whatever his demons are and whatever reasoning for why he is doing what he is doing has nothing to do with me so I can’t make it about me.

Please help!