I felt DD (my first) at 17 weeks and she never stopped moving after I felt that first flutter, it was all that day and kept up until i had her!
With DS (my second, and last) I felt him around 18.5 weeks, felt him that night and a little the next day but then went another few weeks without feeling anything, I rented a doppler because I swore he was dead. That happened for weeks, I would feel him a little for a day or two and then not feel anything for days!