Food?

So I found out I was pregnant Saturday...and now everything I eat doesn't taste the same. I've had two kids and I've never been this bad. I ate a grilled cheese last night and forced it down basically. And I had spaghetti for dinner tonight and I was just not wanting it but forced myself to eat...now I just feel gross inside. I'm only 4 weeks pregnant and I'm basically tired all day and food grosses me out. Two weeks ago I finished a jar of pickles in two days yuck. And was eating a ton..now I just don't want anything. Why?? Does anyone else experience this? And is it normal??