My ex is in love with someone else

3 years a go i broke up with him because he was a coward. I felt like im being his mom and i wasn’t happy with him i knew he isn’t right for me and yet he stalked me after i broke up and begged me to take him back so i blocked him 😒 today i heared from a friend that he moved on and he is desperately in love with this girl. I dunno why but i felt so insecure, specially when i saw her pic and saw she is super cute. Why do i feel this way?

P.s. i colored my hair and people keep saying it doesn’t match my face

P.s. im in a happy relationship