To cut a long story short, I separated from exP when DS was around 1.
The arrangement has generally been a 60/40 split (though there was a long period were ExP didn't have DS at all over night, but I don't think its overly relevant to my AIBU) though I am the "main" parent and deal with all appointments/nursery/child related admin. ExP has had DS most of the weekend up until now as my work has allowed me to spend a lot of time with him through the week and exP works Monday to Friday, so this arrangement has allowed DS quality time with both of us for days out.
DS starts school in September so me spending time with him mid week isn't going to be a possibility so I suggested to exP that we should have every other weekend with DS. To facilitate this we would continue having the same number of nights per fortnight so she doesn't lose out per se.
ExP has flatly refused. I guess my AIBU is should I put my foot down on this as I feel its incredibly unfair and is it worth getting a child arrangement order over? (Or am I even likely to get what I'm asking for)