Baby's movements

I've been sick and I had a bad cough so I took some Mucinex DM because my doctor said it was safe. Today, though, I have hardly felt my baby move. I mean she moved this morning quite a bit but it was all at the bottom of my belly. There was one kick in the upper right side of my belly where I normally feel her. Her movements feel so much lighter than they have felt. Normally they are pretty strong. Is this something that is normal or should I be concerned?