Trying to pinpoint conception!

Hello my name is Alice. Okay....I know maybe I shouldn't even be putting this question up here. But they put all these stupid shows on TV about women not knowing they were pregnant and blah blah so I just need some reassurance. I have been on the NUVARING since I believe January 2011 after having a miscarriage. It has served me well since then. I have my periods on time and haven't had one scare. When I got pregnant the first time I did not receive a period, which is the norm. So on May 25, 2012 I had a regular period on the nuvaring (7 days long, heavy). Then I took it out maybe about a week later and received another period about a week later (also about 6 or 7 says and heavy). Then, and I'm pretty sure this is because I messed up my cycle, I had another period that was also heavy and lasted for about 4 or 5 days. After that, I had unprotected sex with my husband probably about 5 times. Then two days ago I took 3 tests and they all said positive! However the first and second test that I took both took about 2 or 3 minutes to show up. It is more than likely that I conceived just about 2.5 weeks or so ago, correct?

PS it doesn't help that my best friend is a crazy lady and tried to freak me out with "oh you never know. I had a friend that didn't find out until 28 weeks" I'm like oh thaaaaaaanks. :/