What Causes Delayed Periods And Nausea After A Failed IVF?

I recently underwent an IVF cycle and it failed. I am now 36 days into my cycle. Usually I am clockwork w/my period (day 28). After previous IVF attempts I have always gotten my period on time. For the past 4 days I have had slight nausea coming and going all day. Of note I have a son conceived w/a prior ivf attempt. Is this periods' delay b/c of last IVF attempt?