this is completly completly normal, first off teh baby is getting pretty cramped in there now, also babies all lulled to sleep by motion and noise, when your up your moving around and theres noise all the time so your baby will sleep more (which is one reason babies always seem to have night and day mixed up when they are born) and when you lay down your still so the baby thinks its party time lol, not to mention when you lay down it kind of compresses your stomach (which is why even before you show you can ususaly feel your uterus/"show" while laying down) so it makes it a lot easier for you to feel teh movements

however, if you EVER feel something isnt right or even if your just worried and you think your being paranoid, call your doctor, that is what they are their for, its not being silly or dumb or bothersome or anything, its being a good mommy