Fiancé is hooked on drugs

I just feel so broken but it’s obvious he’s always in the bathroom. He goes from really happy to losing it. Every time i go in the bathroom after him it’s like this sweet chemical smell and sometimes it smells bad that I could throw up. I’m just sick I’m dealing with so much. I feel like he hates us or something. I’m depressed and have kids involved like how do I do this? I’m just so broke...