post baby stomach

So my baby is over a week old and sadly he stretched my stomach out so much. He was 13 lbs at birth and after giving birth (which I put on almost 30 lbs) I was weighed and lost over 20 lbs of just baby and placenta! But I have noticed my stomach looks horrible. It's filled with stretch marks (I expected them but I didn't seem them until after baby came out) and my stomach is so loose and just kinda hanging. Here's a pic but will this calm down? And is there anything I can do about the stretch marks or am I too late? Thanks