Hi
Mr "footballer" wants the test because his best friend has chewed his ear about making sure that you arent lying to him and the cute little girl isnt his. The pretator mentality is that if you are having sex with him the who else are you doin.
I dont think that he is wanting to take custody of the child.
He realy doesnt want either family units broken up, he just wants to be sure hes not paying for someone elses kid.
It doesnt mean you can trust him as a lover.
As a former preator myself i can honestly say we are lying sacks of shit when it comes to our genitals.
So just so slow an steady and make sure you cover your ass.
As for the affair side of it, these things happen and well everything now is past tense so lets just think of getting the future more positive for you and the cutie thats the real issue not the fact that you have a misadventure look what has come out of it, your daughter is beautiful and defineatly not a mistake.
Mega hugs and love.
Cheers Pete

Now that I"m home.  I agree with Psychic Chef.
No guilt.  Guilt does NO good for you or your kiddo.
Again, take good care of you both.  We all have had our experiences.  They are for our growth and you got a wonderful gift from your growth experience.  Life is no about not making mistakes, it's about what we do with what we learned. Please don't let yourself go into guilt.  It is an emotion that is not empowering.

ditto.
what tourbi and PyschicChef said.
take care of yourself and your child.
hugs to you.

Go with Psychic Chef Advice.He knows what he says as he sees through.
Tourbi said right about the guilt thing.

You have been getting a lot of advice, but you are the only one that knows what is best for you and your child. He probably just wants to be certain that she is his child.  The best thing to do is ask him what he is doing, why he is doing it, and how does he picture the future for his child.  Open communication is the key to any successful relationship.  It helps if you do not sleep with him anymore.  
Lots of hugs!