Hes deniying my kids are his!!!?

or should i say our kids!!! I have two beautifull boys aged 4 and 2, Their dad hasnt seen them since my youngest was approx 2months old or younger. So anyway, i contacted the csa recently and they called me 10mins ago to ask more details. They say they are very sure they have the right man. She said if he denies that he is the father then he will have to do a dna test? has anybody been through this? Its not about money with me, its just so i cant prove him wrong. omg i actually loved this guy!! Why is he denying our kids? He said he VAGUELY knows me because i dont live far from him but we never had a relationship!! I was with him for FOUR YEARS!! God, why is this so heartbreaking?? Im over him 100% but this HURTS!!! I dont hate him, i actually thank him for giving me 2 beautifull sons and i feel sorry he's missing out on watching them grow. Awwwwwww. Whys he being so silly!! How long is the DNA going to take?? I just want to ease his doubts and then maybe he will want to see his boys.