Why do I get jealous of other couples?

It s been now almost 8 months I have been alone and I am now at an age where my friends have babies, married or settled. But me I am still here without nobody! and d worst thing is that now i even start getting jealous or admirative about the couples I see everywhere, train, bus, on the street.... I think I am depress coz I start eating like a pig! I am really jealous?Why do I get jealous of other couples?
I think that you are jealous, but it's ok not to be married or in a relationship yet cus there is plenty of time. I think you should try to enjoy being single for now. Hope this helps. ^^