Activity is quite confusing to grasp at first, but basically you can only get a max of 14 activity points per every two week period. The new period starts tomorrow, so if you make 14 posts today you will get 14 activity, then if you make another 14 posts tomorrow you will get another 14.
A 'definitive guide to activity' is here: https://bitcointalksearch.org/topic/the-definitive-explanation-of-how-activity-works-495948
Newbie guide with explanations of the time restrictions at the bottom here: https://bitcointalksearch.org/topic/newbie-readme-177133
Guide to member statuses here: https://bitcointalksearch.org/topic/forum-rankspositionsbadges-what-do-those-shiny-coins-under-my-name-mean-178608