Why would a boyfriend act single for years if he says he loves me?

I was in a relationship with a guy for the last 4 years and I knew he loved me or used to know he did ( breakup's driving me paranoid). He pretended he's single to not just girls but boys for the last 4 years. Why would a guy do that if he loves you or what do you as guys think about it?
Why would a boyfriend act single for years if he says he loves me?
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