Advice please

So I was with my ex for over 4 years. I wanted to live together and eventually get engaged and have kids one day with him. Towards the end of our relationship, we started to argue and things weren’t getting better.

He broke up with me in March and it broke my heart so much. All year I’ve kind of been depressed over the break up.

He started dating another girl and has been with her less than a month. I saw on Facebook that she’s pregnant and they are having a baby.

I am extremely upset over this news. And I don’t know what to do. Any advice ?