I am 13 weeks preggy now,and want to know if what is the hard part in my lower abdomen,I can feel it when I'm lying on my back and touching my belly... is it the baby? Thanks

Well, the baby inside the uterus. You're feeling the outside of the uterus right now, and you should soon be able to feel the baby moving about inside the uterus - that starts feeling almost like soda bubbles inside, then becomes more definite. It will be a while yet before you can feel parts of the baby touching from the outside.