Hi and thanks for writing JA
I am sorry to hear about your predicament. It seems somehow these relationships are not lasting or appearing for one of two reasons. Either you are making poor choices as goes prospective girlfriends or you are behaving in a way that runs them off. No way to tell from here.
Do you have platonic friends or siblings who are in relationships who can observe your behavior and give you feedback? Let us know what you think you might be doing wrong here and if you can provide more information so we can help you better that would be great too.