Is there a real reason why every time I get involved with someone I begin to sabotage it and convince myself I don’t have proper feelings for them?

I feel like it may be somewhat related to my last relationship but idk why I can’t stop doing it

I regret it every time but when I’m in the moment I feel so strongly that i should cut off all contact with the person over a feeling I can’t explain

Anyone else have this/any advice?