I agree. As you move further along in pregnancy, the baby will move lower into the pelvis again and your stomach will constantly look different as the next few weeks go by. If hes moving like usual, he is still alive and well in there. He has less room in there as you get bigger and he can feel you moving, he's probably just reacting to your movement. The only reason you should have for concern is if you develop any unusual and large amount of bleeding and cramping or if you don't feel him move at all for more than 24 hours then you should contact your doctor just to be safe. It is common to feel nervous throughout your whole pregnancy, but remember that death in the womb is very uncommon. Try to keep your chin up and push all those worries out of your mind. Good luck!
It is normal to look smaller, baby is probably just in a different place. The further along you are, they seem to make more room. As far as baby moving when you do, I wouldn't worry at all, it's normal for them to move whenever they want, and it doesn't matter that your moving too.