A "lot of blood coming" seems excessive if you were already pregnant then. Yes, you can have bleeding but it normally is light.
It appears as if your doctors estimate your LMP around Dec 27. That's based upon the 2 week and 2 days you said they told you on March 10. Doctors "usually" base dates on your LMP and not the actual gestation.
Normally you would ovulate between about days 11 and 16 of your cycle.
In December, you had sex about day 15 of your cycle. You'd be fertile.
In January, you had sex the week of days 10-17. You'd be fertile.
You don't report a period for February.
The first of February would have been day 28, well past ovulation and you'd be at your lowest fertility - if you weren't already pregnant and you were.
Feb 14 doesn't matter, you were already pregnant.
It takes AT LEAST two weeks for the test to become accurate so you likely were pregnant before the 26th of January.
You'll need a DNA test to confirm but it looks like "someone else" may be the father. The timing does NOT appear to work for your boyfriend - if the dates are right you'd be almost another month along. No form of birth control is 100% effective.
Hope it helps, good luck.