Why? My 9 months old baby is clingy to daddy

I am sad. Idk if anyone is or ever have been through this before but my 9 months old is very clingy to his daddy when mommy is around, he doesnt want me at all. I'm a good mom and I love him so much.. it sucks so badly. I work a lot. When daddy is at work and I'm taking care of him, he seems fine and wants me all the time. I am embarrassed by this. I feel like a failure. I need advises please