Hello, and I hope I can answer your question. Unfortunately it is not possible to know whether you may be pregnant without doing a pregnancy test. The stress of surgery certainly can certainly make you miss a period or two from the stress, and Plan B can also affect the timing of your next cycle. You can feel bloated and have mood changes from missing your period as well as pregnancy, so the symptoms can be similar. So I would advise to do a pregnancy test and if it is negative just give it some time. Also it is still possible to become pregnant even though you have missed your period, so i encourage you to use pregnancy protection. I hope this advice was helpful and best wishes, Dr. Brown