Megan - I started feeling just little butterflies (or wind!!like) m/ments at the end of my 20th week _ I was worried too when i read some peole felt bub at 15/16 weeks but they are all individual arent they. Have you tried a very cold drink- feet up relaxed to see if you can feel anything? This works for me even now when bubby is a bit quiet.
All the best.