I think my baby is ruining my marriage

My husband has always been my best friend. We wanted nothing more than to have a baby together. Now he is here and he is perfect but it seems like now all my husband and I do is fight. I admit I'm protective of our newborn. His mother wants to come over every day and be in his face and wear strong perfumes and tell me how to parent. It seems like every time she's here I'm reminding her of something she needs to change. My husband says I'm being too protective. I'm picking on her.... Today she yelled at me. She called me selfish and stormed out of my house. My husband blames me. He is choosing her side. He says I'm being too much. I'm trying to relax but I'm on edge. Our baby is only 2 weeks old. Please offer some advice. Should I lighten up? How do I lighten up? How do I get my marriage back? I feel hopeless and lost. I feel like the best time of my life is turning into the worst.