Why is he still around?

Me and my partner got back together after 6 months of break up
He kept wanting me back

Thing is.. we got back together last week and found out I was pregnant
And few days later, I gave birth

The baby is definitely his since I never hooked up with anyone else after our break up
But partner told me he still wants a dna test since he's not 100% sure the baby is his

However he still supported me and was by my side through labour delivery of baby
Seeing me and baby everyday
Etc

If he's not sure if baby is his then why is he still with me and baby?
Why is he still around?
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