Is Our Marriage Truly Predestined? Feeling Lonely and Confused

As-salamu alaykum, everyone. I hope you don't mind me sharing what's on my heart. I'm a Muslimah who has always tried to follow the right path-never involved in any haram relationships. Yet, when I look around, I see couples who began their relationships in ways Islam doesn't approve of, but now they seem happy, even married. Meanwhile, I feel so sad and lonely. Some nights, I cry myself to sleep because I feel unloved and isolated. I’ve tried to be patient, but the loneliness is hard to bear. I wonder, is marriage truly written for us by Allah? Are our spouses already chosen no matter what? And if two people marry after having a haram relationship, would they have still ended up together if things had started in a halal way? I'm also scared to even search for a spouse. I struggle with depression and health problems, and I don’t feel confident about my character or appearance. Does that mean I’m not worthy of a good marriage? Islam encourages us to seek righteous partners, but I don’t always see myself as the best person. At times, I don't even like myself. Yet, I see others who have hurt people or acted wrongly, and they seem loved and happy. It feels really unfair. Looking for marriage without knowing someone well worries me-I've heard many scary stories. I know Islam allows us to get to know potential spouses, but it’s not like dating, and there’s no guarantee the person is truthful. I’m not doubting Allah’s wisdom, just feeling overwhelmed and trying to understand. I’m sharing this to get it off my chest. Please be kind and understanding with me. JazakAllahu khair.