I need a serious relationship

I was dating a girl last year and things were going better than any other relationship I've ever been in. She told me she loved me, made me feel confident, and surprised me with by doing little things to make me happy all the time. A few months back , All of that stopped and she grew distant, I found out she was cheating on me, and I ended the relationship. I don't know how to deal with these feelings. Whenever I think about her with anyone else. I feel sick, I've lost all of myself esteem, and having a hard time convincing myself I deserve any better. And then the other day, she sent me pictures of her hanging out with my best friend, This bothered me, because my best friend never even talked to her before we broke up, I confronted him about it, and what he said made me feel even worse. She had been trying to hook up with him. But he said he wasn't reciprocating at all. I feel even more worthless now, I'm not good enough for her but my friend is? How did you with being cheated on, Did it get better for you 😭😭?

No matter who you are, no matter what you did, no matter where you've come from, you can always change, become a better version of yourself.