Am I doomed to keep sabotaging all of my relationships?

Not necessarily. It’s important to stop bad patterns once you realize you’re making them.

It sounds as if you could use some therapy to understand this pattern.

Perhaps you begin to find fault with them when they start coming too close to you. In other words, you are shying away from true intimacy.

But it could be several things. I think you might be happier to stop dating and work with a therapist on your issues.

Maybe you should get into counseling. You may have heard the old saying, “If you always do what you’ve always done, you’ll always get what you’ve always got.”
Maybe you have not found the right person, or maybe you have unrealistic expectations of what a long term relationship looks like after the initial hormone buzz wears off. Maybe, you are just someone who deep down gets bored to easy for a long term relationship.
If you can afford it, you might want to consider a few sessions with a professional counselor to help you sort through your feelings. A good one will help you look at things realistically, and figure out what it is you really want.

It might be good to get some therapy but alternatively it might just be that you haven’t found the right guy yet… you might just need something more stimulating…it might just be your style…do you want long term commitment? But having said that I’m a firm believer in being able to change if you want to, but it takes a long time…even with therapy. I’ve had four years of counselling and I still have relationship issues but I’m learning all the time and getting wiser by listening to and honouring my feelings. Don’t beat yourself up about this but explore it with compassion and an open mind. If you do carry on dating I think honesty is the best policy at the right moment…if you feel like you are going down the same road again I would talk to the partner you are with about your past and how you feel…

I agree with the above answers.
You sound like you might have some inner issues to work out.
Perhaps relationship addiction issues, meaning, you are constantly seeking external validation from men and when the luster wears off you move on to the next target that will infuse you with those good feelings that only YOU can provide for yourself.
The recycling of going from idealizing to devaluing in short periods of time tells me, that the issue lies within you, not the men you are dating.

I strongly agree with taking a lengthy relationship break and getting clear within yourself with the help of some therapy.

I can’t help but wonder if you felt you were in love with anyone of these guys. Some relationships start with a couple thinking they were in love and to some, it could develop much much later.

On behalf of men everywhere, I would like to thank you for recognizing that when you start feeling there is nothing we can do that is right, you end the relationship. Seems to me, that’s when many women decide that things would be better if someone proposed.

There are a lot of things I could say here… but it’s all been said, and there are some pretty good suggestions on here already.