It is "normal" to feel emotional at 4 weeks because your body is expecting your period to come so your emotions will run high regardless. When you dont get it, the other hormones start kicking in, cause mayhem to your emotional state. I cried at hallmark commercials on tv! Haha
I was very emotional for my 1st 2 months. It has subsided since then. I'm now 4 months.
I don't know if normal is the right word since everyone is different, but I experienced weird emotions at 4 weeks