Child maintenance

Hi my little girl is 4 months me and her dad split when I was 20 weeks pregnant I have applied to child maintenance directly because he was being difficult about it. They phoned me today and said he has denied paternity when I called him to ask he first off said well I don’t know if I’m the dad which is the first he’s mentioned anything about her not being his then said I only said I wasn’t on the birth certificate (which was his choice btw I offered he refused to)I didn’t say she’s not mine. I just wanted advice on anyone who has been through the process of child maintenance or knows about it will they directly ask him if the child is his surely the don’t base it upon them being on the certificate or not got a feeling he’s just bulshitting me trying to backtrack.