Wanting to create a contract - been ~1 year with NF

Been working for a family for almost a year now, my main responsibility is 16 month old NK occasionally the older kids 7 & 9 but they are in school. For the summer they go to their beach house and are still paying me full time with occasional days I’ll be working. I never made a contract with them when I started, it all started fast and I got thrown in and at the time I really needed a job. MB is pretty all over the place, house is messy, she doesn’t follow set times, etc but they pay me well and on time.
I am wanting to create a contract now and don’t know how to bring this up. I don’t want to feel shamed for not having done this before - I was in a bad place in my personal life and really needed a job to get out and I did. So what do I do?
Thanks in advance!