SO and money for bills…

How do I put my foot down with my SO… all my bills each money are about 2500.. I’m a nurse but I’m also in school further my education so I don’t work as much right now. I am able to cover the bills each month but I constantly am running into the problem of not saving any money… my SO has been living with me for 4 years. We have a one year old together. His communication is piss poor when it comes to bills. He know how much my monthly bills are but never ask me how much I need or what needs to contribute for bills. I guess he was never held accountable in previous relationships so he just doesn’t care🤷🏾‍♀️ He thinks giving me 400$ or less each month is enough. When I constantly tell him I need him to contribute more. He does work so thats not an excuse. I have tried to sit him down and say hay I need more help, I’m not working as much.. i remember a few months ago I had to nag him to death about giving me 700$ because I was only able to work a few shifts because of school. But this is crazy and unacceptable.. he never hand me the money in my hand. He always sit it down somewhere for me to stumble upon it and i hate that