Menstrual changes after Lipo/BBL?

I am 5 weeks post lipo/BBL. I was scheduled to have my period 2 days after my BBL and it came right on time. I had a regular period with no issues. I was then due again for my period 2 days ago and it never came. I am NEVER late. It comes every 28 days like CLOCK WORK. Just saw my GYN last Thursday and had my annual pap, so I'm pretty sure my doc would have told me if I was pregnant, so I don't think that is the issue. Any input on what might be going on here? Thanks!