Scared of being alone forever

So everyone and their siblings are getting engaged these days.

I'm 24 and I am in a long term relationship but we recently had a bad hiccup that I'm still recovering from emotionally. In the past few months there's been such a wave of engagements, babies, house buying and whatnot and I am ridiculously anxious.

What if I never get proposed to? What if we break up? These days it feels like if you're single at my age you're doomed for a sad lonely life, it's ridiculous.

My dream is to get married and have a little dog, I'd want nothing but the sense of someone formally and legally choosing me, so everything around me have really got me down...

How can I deal with this?