Relationships

How can I feel better about not being in a relationship?

My girlfriend of 4 years broke up with me a few weeks after accepting to marry me. She said she didn't expect our relationship to on this long (she wasn't serious from the start, whereas I was all in from the begining)... she was essentially using me all this time...
Anyway it's been 2 years now, I'm turning 27 and yet feel sad that I'm not trying to make a family anymore, I wanted to have kids a little younger than I am now...

All my friends are married with kids, my younger cousins are settled, even my younger siblings, but I feel alone and unmotivated to persue a new relationship...
I'm a good looking guy, still have had some girlfriends since the breakup but never anything as serious as before..

How can I get over this feeling of sadness
How can I feel better about not being in a relationship?
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