dont't feel this way. I faced the same issue before. I felt so helpless that time too. But after 1 - 2 months later, he will be fine. This is what happen to mine. Since you are breastfeeding, I'm sure the bond is strong. Talk to him more often, he will recognise mummy's voice.
I think maybe is the way we hold them, afterall we are all first time mum. mother in law is definitely more experienced. I also realised the tone of voice we used. Babies love high pitch voice.