Yup thats normal. Baby still has heaps of room to wriggle round in! I'm sure you'll start feeling stronger kicks over the next few weeks :)
Yes they have lazy days. Shouldn't worry about it until you're 28 weeks and after that if you don't feel him/her move 10 times in two hours to go in(:
I'm feeling strong kicking and I'll be 22 weeks tomorrow.. Your baby starts sleeping more too so the days he doesn't move as much is because he's probably sleeping. I have my sons sleep schedule down pretty well.