I think one problem is that you 2 went from living long distance to living together! A better idea, if he wanted to move to be nearer, would have been to live near each other, but apart, and start normal dating. It seems to me your partner wasn't really ready for full on living together.
Maybe if you got your own places, you could still date him from time to time, as one of his partners, not his nesting partner. Then you wouldn't need to be so aware of his issues, his emotions, when he wants or needs more variety (for whatever reason).
I think of the usefulness of variety in our lives. If we eat a large amount of one food, we get full, we say we couldn't eat another bite. But if we are offered a different food (with different nutritional value), we suddenly have an appetite.
If a male rat has intercourse with one female, he will finally leave her, satiated. But if he is put with another female, he will become aroused again and eager to have sex. And the pattern will repeat, and he will fuck one female after another, until he is well and truly exhausted. This is nature's way of getting as much of his DNA out there as possible.