HCG levels??

Hi everyone! I just need a little advice :) My last period (17/03) was very VERY light. not enough to even wear anything, I took it out and there was basically a drop, and that is what it was like for two days! (usually im very heavy for at least 4) My boyfriend and I assumed my birth control was making it light and didn't think much of it until I found out I was pregnant this month! Based off of that "period" I would be 6w1d today, but if that was impantation and not a period, I would be almost 1/2 weeks more than I thought. I went to the doctor at 5w2d and I got my levels back, it had said 42,156! Obviously I'm not a doctor but that seemed high to me for being so early! I guess my question would be, what were your levels around that time? Would you say I'm farther along than I thought?! I got for my ultrasound this weekend, but it is still bugging me now!! Thanks in advanced for the advice!! :)