After the IVF

I am now 19+ weeks and my pregnancy books have mentioned that I would be feeling fetal movements as early as 16 weeks. Well I haven't noticed anything yet like my friends and books have described...bubbles, fluttering, feathery floating sensations. But the last few days I have noticed that I keep feeling a heavy sensation like a rock in my lower abdomen. About 2 days ago, it felt like it was rolling here and there in my abdomen. Today I realized, hey, that's the baby moving. Its not gas, and I don't have to poo. Its not a piece of poo...its my kid! Heavy rocks rolling...not a bubble or a feather or stuff like that.