It sounds, from almost no evidence, like the first guy is a bit more likely than the second to be the dad. But you will need to get some better medical input to even come close to being sure. Go to the doctor now and get an ultrasound scan. If your own doc won't do one, find another doctor. You're at just about the best time to be able to try to pinpoint conception using the baby's measurements as seen in an ultrasound; later in the pregnancy (even by a few weeks) will not give you the precision you need.
Tell the doctor that you can't remember the first day of your last period, and that you would like an estimated due date based on the baby's measurements and developmental markers as shown in the ultrasound. When they give you the due date from the ultrasound, go home and count back from that due date on a calendar 266 days, or use a conception calculator online. Don't let them just tell you a number of "weeks pregnant" and leave it at that, you need an Estimated Due Date. From it (if you get it right away from an ultrasound) you can come up with an estimated conception date.
If you wait, by pregnancy week 12, any estimates of conception dates based on ultrasounds will be plus or minus 7 days, meaning they will not help you decide who might be the dad. And the margin for error gets larger as the pregnancy progresses. So don't wait.
In the end, you will need a DNA test. (The dates of the two men are only a week apart, after all.) But if you get an ultrasound this week, you might be able to figure things out with a little bit of certainty.