I'm 24 weeks and don't feel there's much routine or regularity to the movements yet. There was a couple of weeks where I felt barely anything, having had loads of movement before. I went to a Skunk Anansie gig at the beginning of February and after that felt nothing for a few days. I totally panicked because I thought the gig had been too loud for it!
Eventually felt some dull bumps sort of every other day, but not like the prodding I'd felt previously. Spoke to friends and we figured that baby had turned around to face inward, so the duller bumps were its back pushing out rather than its arms and legs. So that can happen too - baby just gets in a position where its movements aren't as strong on the outside.
Do call a professional if you're concerned and have your mind put at rest xx