Long time lurker looking for an external perspective on my relationship.

Both late 20s and been together for about 3 years. Lived together for the last year. First became aware of mrp about a year ago and quickly realised I had been treating her like a unicorn and it resulted in arguments over what I feel is a load of crap. Predictably I'd talk too much and express my feelings. These arguments/moods seem to occur every few months and were largely around her telling me she is loosing her spark whilst with me, I'm generally horrible, even as far as saying it's abusive when I don't want to speak to her when she's in one of these moods. Past year I've just kept quiet and kept my distance. She keeps accusing me of not asking her how she is when she gets down. That isn't true, she just says she's fine but flips out a few days later accusing me that I don't care. Often during these moods she says she can't be with someone like me and needs someone that understands her. Next day she says she loves me so much and apologises.

Over the last year my frame has become pretty solid, I'm stoic when she is moody but when it's good we have fun and enjoy being together. 90% of the time it's all good in my eyes.

Other aspects of my life are going well. I have a good career, play a sport to a high level and lift 3 times a week. I'm in good shape and she tells me that. That being said sex has been reducing over the past 1.5 years.

That's it in a nutshell. She suffers from "anixety" and has been on medication for it in the past. I know I was too much of a nice guy in the first year, trying to be the perfect boyfriend and that still lingers with me. Any perspectives on this would be appreciated