Generally, the tests take 10 days. I suppose if you knew a scientist they could run a test for you, using DNA from your boyfriend and your baby, but DNA can't be run in an hour, according to my friend who works in investigations for a sheriff's department.
I think you should sit him down and say "OK, you think I cheated. I know I didn't. So, let's go and get the DNA test, and we should get results back in about 10 days. But let me ask you now, what happens to all of us when the test shows -- as it will - that this is your child?"
Then listen to your answer. It sounds like your boyfriend doesn't really want to be there and is looking for an excuse. You know this is his child. So what happens next? That's really want you need to find out.
Please learn from this. Get on good birth control, like an IUD or an implant, until you are married, so that you don't have to go through this emotional drama again.