How do I become girlfriend material?

I don’t get how some girls make it to girlfriend. All my communication with guys has always been something like placeholder and backup plan. I get told I’m very gorgeous and beautiful but still find myself in low positions like that. I try my best to not put myself there but still end up there. The guy I’ve been seeing for almost 6 months I thought saw me as a girlfriend until we were having a deep conversations about exes. I told him how he is one of longest guys I’ve ever talked to and guys usually get bored of me within two months. He told me I wasn’t a boring person but I come off as a casual person or temporary fun. The whole time I thought someone had finally liked me. He’s been treating me like a back burner lately and only hitting me up likely when he’s bored.
How do I become girlfriend material?
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