Baby movements!

Bethany
I will be 19 weeks tomorrow.  Around 16-17 weeks I began to feel my little guy making movements, and it felt like little butterflies.  Right about 17.5 weeks I started feeling kicks.  They were little thumps but strong!  This past weekend we moved and I lifted some heavier things.  I noticed I didn't feel my baby moving very much after that.  It's been about 4 days and I hardly feel anything and when I do, I can't tell if it's a gas bubble or my baby.  Yesterday I took a nap and when I woke up I had a sharp ache
In my lower right abdomen. I laid back down and it eventually subsided.  It happened again when I got out of bed this morning.  I'm thinking maybe it's my muscles stretching?  Anyone else have these issues at week 19? I expected to feel him move more, not less.