It sounds to me like what you're saying is: "This is my relationship situation right now. What do you think is going on?" One thing steps out front and center. Your boyfriend chooses women who trigger your fears.
The reason I point this out to you (other than the fact that I see it) is to ask you if you're interested in taking a closer look at this. Are you willing to consider the possibility that one of the reasons you are attracted to your boyfriend in the first place is the fact that he is attracted to women who trigger your fears?
Whenever someone "triggers" you, you have the opportunity to feel the emotions that are triggered within you. That is always an opportunity to get to know yourself better. Those who have the courage to look right into that experience, and therefore look right at themselves (instead of looking at the person who did the triggering), usually come away from that experience knowing themselves better.
A big part of happiness is knowing yourself really well. I see problems in life as opportunities in disguise. Part of my happiness is the feeling of curiosity I get when I'm looking through the problem to find the opportunity. It's like a treasure hunt. The opportunity is always there. Most of the time it's something I hadn't even thought of. Going with the opportunity I find usually feels like an adventure.
I'm telling you this because I know from my own experience, and talking to others I know who are genuinely happy with their lives, one of the things we have in common is we each know ourselves very well. The reason we do is because life gave us lots of opportunities to look at our unresolved emotional stuff. A lot of those opportunities included feeling fears that were triggered by the behavior of others. We each grabbed as many of those experiences as our courage and energy could handle, and used them to get to know ourselves better. You can too.
The women your boyfriend is attracted to are giving you the opportunity to look at yourself and the emotional pain that is inside of you each time they do something that causes your boyfriend to do something you don't like. As long as you're experiencing those triggers, use them to get to know yourself better. Look at the things "she" does that cause him to do something that triggers a fear in you like she is literally pointing you in the direction you need to look to understand yourself better - because she is.
What do all of the things you feel when you are triggered have in common?
What is the common fear?