I hate being single? I don't know how to cope?

Every friend of mine is in a relationship. And I'm just. There. They always post pictures of their dates and stuff and their partners and whatever and I have nothing to contribute but pictures of my cat and pictures of a drink I got from dunkin donuts. This feeling is horrible. It feels like no one cares for me on a deep personal level. Like I know that obviously there are people who care about me, but there's no one that wants to invest in me. No one that's determined to get to know me. Learn how to love me on a personal level. There's none of that and it's just so unsatisfying and it makes me wonder what could be wrong? Everything came so natural to my best friend. She gained a crush, had it for months, then her crush actually messaged her and told her his feelings, then she finally came out and told him hers, and they instantly clicked. Me, however? I gain a crush, I tell them, they shrug it off, or I barely get a Reaction, and that's it. I don't overreact, or start treating the person bad when they reject me. I just swallow it, then make a dumb little joke afterwards, and then that's it. Even though I'm absolutely crushed and they don't really care. Not that I blame them. I just want to feel cared for. I want to know that I'm a person worth loving. Because I just feel miserable and unwanted.