Tubal ligation...kinda long sorry

I had my second baby on April 28 via c-section and got a tubal ligation at the same time. Hubby and I both agreed we were happy with 2 kids. We waited 10 weeks pp to be intimate again. We have probably only been intimate a total of five times since and my lo is 5 months now. My question is lately I have been feeling really nauseous, tired, movement in my tummy and cramping but no period. Sunday, I had clear discharge and it has continued. Has anyone else had these symptoms since a tubal ligation? Can I possibly be pregnant wether it be a normal or ectopic pregnancy? My ob told my hubby and I that the body is amazing and will sometimes heal itself and the tubal will fail. She did say it was rare though. I also have an aunt that got pregnant with her 4 baby after having a tubal. I did take a pregnancy test and negative. Thanks