What is causing my fainting/near-fainting spells?

I'm 25 years old, healthy, no significant medical history that relates to my current fainting/near-fainting spells. A week ago, when I swallowed my pill, I felt chest pain so I sat down and then it started to get worse and I could hear the noise fading and all I could hear was buzzing. I ran to the bathroom because I felt queasy and felt as if I had to have a BM and then I just blacked out. I woke up and my fiance put me back to bed. I had a cold sweat and was pale. I went to the doctor and she did some blood work to see if I had anemia but turned out negative. She ured me that it wasn't cardiac related instead due to my low baseline blood pressure, anything that could trigger my blood pressure to go down even just a few points, would cause me to faint. This makes a lot of sense to me so I left the hospital and felt better that it wasn't any major underlying factors that caused this to happen. Today, I had another episode. This time I didn't black out, just felt all the same symptoms I did previously except for the black out. I notice that it happened both times in the morning 15 minutes after I wake up and both times, I had cold sweat. What could be causing this? Is this something to be concerned about? Please advise.