@KatieRobin, you are describing exactly how I felt in my marriage. I was adored at the start, it felt as if we had a connection and he was emotionally available but looking back there were signs. The switch of his behaviour occurs not because of you but because of HIS fluctuating emotions.
You don't need to label him but this article by Elinor Greenberg PhD might help to shed light on what could be happening.
"Trying to satisfy a Narcissistic partner is similar to learning how to become a tightrope walker —a step to the left and you fall off and a step to the right and you fall off. There is a very narrow, almost impossible to balance on sweet spot where you are temporarily safe. But…you cannot stay still and every step forward presents you with the same exact problem. Everyone eventually falls off the wire.
Narcissists do not have stable inner self-esteem and need external validation to survive. They are walking their own tightrope too! When they are in an intimate relationship, every move their partner makes affects the Narcissist’s stability.
The Real Issue Is Validation
As Narcissists react to how their partner’s attitudes and behaviors affect their self-esteem, what feels validating can change very quickly. One moment they are feeling their self-esteem rise because they are chasing you and you are independent and they perceive you as just out of reach. “Getting” you to stop running and be “theirs” then feels like a big achievement. At that moment your independence is valued—but only because it temporarily makes “capturing” you more valuable to them as an up-regulator of their self-esteem.
Now the Narcissist is in a bind. If you stay independent and sometimes disagree with their opinions or do not do what they want, they feel disrespected by you. They feel devalued and get angry and will pick fights.
If you submit to them, they will again temporarily feel good and get another uptick to their self-esteem. But….if you now give in and become dependent, your value lessens for them as a status enhancer.
Submission = Lower in Status
Lower Status = Less Valuable
There is almost no way you can avoid being attacked by a Narcisstic partner. You have the best chance of surviving in the relationship by deciding where your boundaries need to be, not allowing yourself to be abused, and being realistic about your partner’s limitations.
Narcissists cannot feel pleased with themselves for very long. They certainly cannot give you the continuous love and approval that they cannot give themselves. You could jump through hoops of fire trying to please them and that, too, would not be enough to keep their interest and approval. You would be getting burnt for nothing"