My first reaction to your letter was that he has another relationship.
There is Not Much More that You Can Do
That might be too cold. But, he clearly has other interests on Saturday and Sunday. That's bothering you. If that's bothering you and you've told him that it's bothering you...then there's not much else you can do.
What are these other interests? Is he pursuing them because he needs a part-time relationship only. Are you okay being part-time if that's what he really wants?
I think what's normal is what works for both people. Your dissatisfaction is coming from more than just "time." Maybe you don't feel like a priority in John's life. Maybe you think that John is not putting enough effort into the relationship. Maybe there are other ways that you feel John should be contributing but he isn't. Is he listening attentively to you? Is he affectionate enough? Is he paying enough attention to where you two are headed? Are his ultimate goals the same as yours?
The time issue can be tricky. It sounds like you want more of something, be it time or something else. I suggest you look more broadly at the issues and talk with John about what you two can do to make you feel more satisfied.
It's not just "your problem." Relationships take the care and attention of both people.