Can anyone help me with the math?

Just FYI, no i didn't cheat, that's not why I'm wondering. I just found out yesterday that I'm pregnant. My LMP started November 22nd, give or take a day, I'd stopped trying for a baby so i wasn't exactly perfect about logging my period start days. I often ovulate late, like a week late. Last time i had sex was approx Dec 9th, before my husband deployed for the month. I decided to take a pregnancy test yesterday, because i started bleeding about 4 or 5 days ago, but my "period" was so light that it was suspicious. Turns out, faint line on 6+ tests. Being that it was new years eve, no one was open except urgent care until tomorrow. I went in to verify pregnancy, and ask about the bleeding. It's been all brown discharge the last few days, so old blood, and i know it's nothing to really worry about yet. I had labs drawn yesterday and got an HCG of 19. They said I'm probably only 3-4 weeks pregnant based on the numbers. Knowing what we all know, LMP on 11/22, last intercourse on 12/9, semen can live for 5 days after sex, that i usually ovulate in week 3 but could've been earlier, it takes 9-12 DPO for implantation, and HCG was 19 on 12/31 and doubles every 48 hours, when do we think i ovulated/conceived? I'm trying not to worry, because there's nothing i can do or know until i have more labs to check levels. But low HCG numbers, spotting brown for the last 5 days, and no doctor's office open until tomorrow, i just need to ease my mind a little. Thanks, you beautiful ladies, and happy new year!