What I do when Im concerned- lie on my tummy eith my hands below my tummy and press it a bit. She quickly starts moving....
I feel my baby on a regular schedule since 21 weeks. I'm now 24 weeks. There are still days where she's quieter. Try playing music, makes my lil one go crazy! Sometimes I'll also find she's flipped around or kicking downwards so it's barely noticeable.
I'm 23 weeks 3 days and haven't felt my baby kick on a regular schedule as of yet, and from what I've read, I shouldn't be concerned about it for a few more weeks at least. If you're really concerned about not feeling your baby like you have been (and especially if you're 26+ weeks along), then give your doctor a call since answering your questions and addressing your concerns is part of his/her job. Also, have you tried drinking a cold drink or resting with your feet propped up during a time when you've felt your baby kick a lot before? Those are a couple "tricks" I've read about to get your baby moving for a bit.