Can not access my site using WWW or HTTPS

I have created a site with gitlab page.
and attach with my page with custom domain(my own domain name).
with A name and Cname. and i am also using cloudflair free ssl.
but now when i access my site with www it is showing gitlab 404 page
and when i am adding https it is showing Your connection is not private error.

i can only access with

can any one please tell me where is the problem and how can i solve this.