I feel like everyone is moving forward

I an recently out of a 4 year relationship and being single feels strange and awkward. All of my friends are in serious relationships and talking about babies and marriage.. I was as well but now I'm back to the beginning. I don't know how to handle helping my friend plan her wedding anymore. I feel like there lives are on track and mine has sudden derailed. How do I be a helpful friend when all wedding talk does to me is make feel like a failure?