Shocking BFP.

Hello. I’ve been doing fertility treatments for around 5 months and tried naturally 2 years before that. I have PCOS and irregular periods My dr asked me to get another blood test today as I’m about 4 weeks late and I’m pregnant. Still in shock! I tested two weeks afo aswell and it was negative. Now the thing is I didn’t have a period and my HCG level is 137. Could it be that I ovulated again? Otherwise I’m concerned my level is very low. Day 1 of my last cycle was 1/12 and ovulated on 13/12 with the help you of Letrozol and trigger shot. I think I just need to put my mind at ease