Understanding the FA when my own attachment style is Anxious

There’s something amiss here. What have you left out? Was the relationship going up a notch? Had the expectations changed? I know with me, something has to change for that to happen.

This is a great summary. Also, it sounds like the ex came back in the picture, which has nothing to do with you either. However, the way he chose to handle it was to pursue it because you two are in a situationship: no commitment.

I agree that it is far more important to understand your role in this (not what you did to cause a change, but why you'd agree to something casual if you're looking for a more serious relationship in general), but I'm going to add a bit about the bigger context of the casual, uncommitted coupling. Usually the only reason people choose to get involved in this way is if they are emotionally unavailable to begin with. Insecure attachment style inherently means emotionally unavailable, because there's a struggle to trust either yourself or someone else or both, a struggle to be truly authentic and vulnerable, a struggle to communicate, and a struggle to have healthy boundaries for any insecure attachment style, AP, FA, and DA. Other reasons people choose casual can include they are temporarily unavailable because they are not over an ex, they are temporarily unavailable because they will be moving somewhere else or are only visiting and find it impractical to build a lasting connection but still want sex and companionship, they have a dealbreaker with the other person and know it's not what they're looking for but are willing to spend time enjoying sex and companionship, or they really want more than the other person is offering but hope if they stick around and build a sexual connection then they can change the other unavailable person's mind (this change generally never happens).

In particular, FA have issues that lead to fear of a serious, mature, committed, long-term relationship. They get very overwhelmed by being too close or too far from someone and, if they are unaware about why and not working on getting more secure within themselves, then they will be seeking a relationship that does not scare them: one without any real commitment that allows them to have one foot out the door. One where they are not at all responsible for their partners' needs and have freedom to do whatever they want, but they still enjoy their partners' company, sex, validation, companionship. You cannot change this, because only they can decide if they are ready and want to change it for themselves. Sticking around for a casual situationship will not build a committed relationship, only a messier one as both people have feelings that get more invested but still lack the tools or ability to have a healthier, committed relationship.

As you can see, none of this is about you beyond you choosing someone who isn't committed to you, isn't openly talking to you about progressing the relationship, and isn't building that commitment with you. For AP, who you choose and the behavior you're willing to accept is a very important part of the equation. Choosing someone unavailable will always end in you pushing down your own needs, trying to emotionally trust someone you can't which becomes a self-fulfilling prophecy of repeating these types of dynamics, and getting your heart broken. The key is learning to trust yourself more, feeling good about yourself, not abandoning yourself or ignoring your own needs because you're afraid they're "too much" for someone else, and not accepting less than you want or deserve. Undoing past trauma and fear of abandonment is how you start to tackle your own AP style and begin to work on getting more secure, which naturally evolves so you are no longer attracted to situationships and similarly unavailable people.

In this specific situation, disconnection hurts, but I'd highly recommend ending it. He may panic that you're leaving, but that's due to a fear of loss and loss of options rather than because you're right for each other. But this is absolutely not going to go anywhere except towards hot and cold chaos, pain, and drama. Most of us on this forum have been there at some point and have a lot of experience with this. And you can choose to go through it if you want, but getting some help with your own AP is where the answers lie, not banging your head against the wall hoping a mismatch in insecure attachment style pairing (anxious-avoidant trap) will change and get better when you've only been casual for a little while to begin with.