Regarding counting back from the biometry measurements, nobody ever said you had fabulous wide margins of safety.
It seems more likely to be the second guy than the first because various pieces of information suggest ovulation at or after the 2nd. This is why I asked if you had been testing before the 2nd, if you had no LH surge before the 2nd and then saw it surge on the 2nd, that is a helpful indicator. But if you had not been testing at all until the 2nd you would not know when your surge began. (I would not refine too much on when the mucus discharge was, sometimes that is variable.)
The other problem you have is that your first ultrasound was pretty late for this kind of use. That is why I asked, when you said your "last" ultrasound was in your 9th week, when your first one was, hoping it was earlier. After a while the ultrasound can be off by a few days and is not that helpful. Basically, your ovulation test strips are your most helpful piece of information.
That said, these are razor-thin margins of safety and it would not take much to indicate the first guy. Obviously you would have been a lot better off not having unprotected sex with two guys in one cycle, if you were serious about not putting yourself into a difficult situation. Or at least, you could have had the events more widely spaced within the cycle. But what is done is done, and now you have to do what you can to figure things out.
Your info suggests the second guy is the dad, but you will need a DNA test to know for sure. Even if you think you know, testing is the only fair thing to do for both guys and the baby as well. You can get a prenatal test done for lots of money (use Ravgen or the DDC), or you can get a test done after the baby comes for about a tenth as much. You will need a post-natal test if filing for child support. In any case, whether you test before or after the baby is born, test with both men. Then one man's "yes" will prove the other man's "no." And don't waste any money on a drugstore test. Ask the family court in your area of jurisdiction where to go to do a test.
Was February 2 the first day you used the ovulation test strips?
More likely to be the second guy than the first, since the ovulation testing that you did indicates ovulation at or after the 2nd. Have you had an ultrasound? If not, get one now, and ask your doctor for your estimated due date and ask him or her to use only the measurements and growth markers of the baby to make the count, not the first day of your last period. (To be sure of this, you could tell your doctor that you don't remember when your last period began or that it's irregular.)
Get the estimated due date (in other words, a calendar date), not just a number of "weeks pregnant," and then take it home and count back 266 days manually on a calendar (or use an onine calculator for determining conception). That will give you an estimated conception date. If it is earlier than the 2nd, you would have a problem ruling out the first guy, but it sounds like it will be after the 2nd.
Be sure to get the ultrasound soon or the data will not be useful, because as pregnancy goes by, ultrasounds get a margin for error if used for this purpose. Now is when to get the scan.