How early cam you start having pregnancy symptoms?

How early is it possible to start showing pregnancy symptoms? Im 2DPO, but I swear my sense of smell has kicked into overdrive. I usually am not bothered by smells at all, sometimes can't smell things my husband can. But today, someone 's popcorn had me nearly throwing up while at the movies. Popcorn usually doesn't bother me,and can smell good. I know smell is a pregnancy symptom, I just have a hard time imagining it can hit me this early. Anyone else experience this?