You're saying that the reason you didn't question that the second guy is the dad is that the first guy didn't ejaculate? Sorry, but that's a false assumption.
If a guy has ejaculated recently, he can have live sperm hanging around in his ducts and urethra from the earlier ejaculation. It's a warm environment, and sperm can live a while. (In a woman's body, it can live several days, and there is no reason to believe it won't live at least a day in the men's ducts.) When he gets a subsequent erection, his Cowper's gland emits pre-ejaculatory fluid (you've probably heard of this as "pre-cum") and it will ooze out of the tip of the penis even before he has ejaculated. There are millions of sperm in one ejaculation. So if guy A had some spermies hanging around and they took the pre-ejaculatory-fluid bus ride into your body when you had unprotected sex, plenty of sperm from him could have gone into your body whether he ejaculated or not. If so, they would have still been alive and viable when you had sex with the second guy.
The guy who ejaculated in your body and didn't pull out has the chance of putting in more sperm. But getting pregnant only takes one sperm. Lots of women have gotten pregnant without the man ejaculating in her body. I'm sorry but that's not enough for you to be sure the second man is the dad.
Because you didn't mention it, it sounds like you don't know if the first guy ejaculated or had a wet dream or anything in the time period before having sex with you. (And, unfortunately, at this date he probably can't reliably remember.) All I'm saying is, that you can't rule out the possibility that the first guy is the dad.
If you have the hefty price, you can get a prenatal DNA test; if you do, please test with both guys. (We get so many letters in this community from women who are freaked out because they only tested with one guy and then can't bring themselves to believe the results. You don't want to be out a ton of money and then not believe the test just because you're anxious.) Or, for about a tenth of the cost of prenatal DNA testing, do a DNA test when the baby comes. (As before, it is better for your nerves if you test with both men. One gets a yes and the other gets a no, meaning one test confirms the other.) The good thing about the post-natal test besides its affordability is that the courts will accept those tests as legal proof of paternity, as long as you have gone to a lab approved by the courts. (At-home mail-in DNA tests aren't approved by the courts, don't waste any money on those.)
The only thing in favor of the second guy in the information you give above is that all this time you have been sure he is the dad. If this is simply because he didn't pull out, it doesn't mean a lot, but if it comes from your women's intuition, you'd be surprised at how often that proves to be correct. We've had women write in who were sure their boyfriend was the father and ones write in who were super worried he wasn't, with no more proof than you have, and more often than not their intuition was correct. Not saying always, though.
I'm really sorry, sweetheart, but you won't get a firm answer until the DNA test. The guys were both unprotected and were only a day apart. I wish I had better news for you.
Annie is correct saying either guy could be the father, the incidents were both close to ovulation. Based solely on who deposited the most sperm, I favor Guy B by a large margin.
As expected, Guy A was excluded.
That's good news! And I'll bet Guy A is pleased, as well. Now all that is left is getting the test with Guy B for legal purposes after the baby is born.