if you can't agree on arrangements to spend further time with your child, then you can take the legal route and get a court order. it does not sound unreasonable to ask for 3 nights a week when you already have 2. its common for courts to give dads half of the school holidays if you ask for it. fri-sun every other weekend. some time in mid-week etc.
Before going to court, you'll need to attempt mediation, so it's just possible you'll be able to agree something there. Might be worth trying for 50/50 at mediation, but be prepared to settle for less - that way you are giving a concession so might get what you are actually wanting, ie 3 nights.