Fianc? (28/m) is possibly doing drugs and completely spiraling. Help.

This is going to be long and kind of strange so please bare with me.
I?ve been with my fianc? since 18. I?m 26 now and he?s 28. We got engaged last July. We have a small baby girl.
In October, my husband took on a new job in finance. He?s been VERY stressed out. The job is much more high stress than his last job in means of demands and general time on the job. Even when he?s not at work he?s still there mentally and it?s all that he talks about. I don?t even know if my daughter recognizes him as a parent figure...he?s just there. They expect him to work 12 hour days and always be by the phone if they need him. I?ve tried to be supportive but there?s only so much I can do.
I started to notice that he hasn?t been sleeping. At all. His eyes are constantly huge and he talks a mile a minute when we are together. I thought at first maybe he was just REALLY high strung from work. Then we started having money issues. He took this job for the better money but now we are struggling to have chicken for dinner and food for daughter. I?ve had to start baby sitting out of my home to provide for her and I. Fianc? is in the bathroom ALL the time when home. Like every 15 minutes ALL the time. I haven?t found any paraphernalia but I?m highly suspicious. I grew up around addicts...I know how it looks.
He?s also started leaving the house at weird times. I?ll wake up at 3 am and his car will be gone.
I?m worried he might be having a mental break down and I?m pinning it on drugs but I can?t shake this gut feeling. I want to help him. Please give me advice, I am scared and don?t feel comfortable divulging this to people I hold near
Tl;DR- fianc? is displaying strange behavior after new job. I am scared for baby and I


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