Dating with mental health.

Hello,I have been single now for about 3years and started to give dating another try. Their is a guy I have been talking to for awhile and is taking my time to get to know him,but when do you think it’s the right time to tell someone that you struggle with mental health.So their may be days that I may feel sad for days,etc. I feel that who every I choose to be with in the future should know,cause they may not want to date someone with mental health. Any advice is appreciated,thank you.