trust your body, it is good at telling you when you are doing something you shouldn't be. The lying on your L side thing can help when you are very pregnant - and by then your body will know itself not to lie on your back, it will be uncomfortable.
It sounds like you are doing all the right things and your scan will be exciting, you might see babies face.

With all the information on the internet and some sites not accurate, it can sometimes be good to ask your doctor if she can give you a few good sites to look at?