Passed Out 3 Weeks Post-Op Tummy Tuck, is This Dizziness Normal?

I had surgery 15 days ago. Two nights latter, at home, while I went to the bathroom I started feeling dizzy. I sat and blacked out. My girlfriend said I rolled my eyes, cringed my teeth and peed myself. About 8 minutes later I came back. I'm not feeling any sequela. Doctor said it was a simple faint due to a drop in my pressure, but a doctor friend of mine told me fainting doesn't loose your sphincter. I have a neuro scheduled to Monday but am concerned. What was that? BTW, I'm in Brazil. UPDATE:  Two doctors friends of mine were suspecting cerebral embolism. The neurosurgeon said it was a convulsion, probably due to a latent cerebral dysrhythmia (since I've never had it and none of my previous exams showed any sign of it) triggered by the stress caused by the surgery. He asked for exams to confirm, which I'm still to do. The plastic surgeon is still insisting on “just a drop of pressure” SECOND UPDATE:  I have gone through an MRI and a EEG both of which came back normal. There was no signal of embolism or any brain damage. I went back to the first neurosurgeon and this time he said I could have had just a drop in my pressure OR an dysrhythmia episode (in which case we would have to wait and observe for another attack in order to confirm). I remember he said at my first consult with him that rolling my eyes and  cringing my teeth were clear signals of convulsion. This time he said it was not, and that it might have been just the pressure thing. So I've decided to see another neurosurgeon. This one completely disregarded the others suspicions and said everything pointed out to a suddenly drop in pressure due to the surgery stress and the fact of me having stood up very quickly. He also said that I was out for so long because I blacked out while sitting which prevented me from falling and having my head lowered to my heart level. So, what do I do? The pressure drop diagnostics seems credible? He assured me it was just this, but I'm still a little bit concerned. BTW: It has been more than a month now since this “attack” and I've not felt anything strange since.