What Causes Swelling On Cheeks After Child Birth?

I have recently given birth to twins and my face was fine up until about 4 weeks after giving birth and now it keeps swelling up my cheeks look puffed up and i look like ive got a double chin its really getting me down i dont expect my body to be back to normal for quite some time but my face is getting me down and i havent put weight on ive been eating healthy and getting exercise plesae can you help