What Causes Sudden Drop In BP,fast Heart Rate And Body Tremors?

I am 24yrs old and i have untreated, slightly high blood pressure, avg 123/87. But I have this problem thats gone on for years and I'm searching for the answer (my dr told me it was a mystery..). About a half hour after eating (usually in the morning, but can happen anytime, its very unpredictable, and I can't figure out what the foods have in common), I get very weak, where I cannot hold myself up, even sitting, I have to lay down. My heart pounds, and my heart rate goes up, I get really shaky, cold chills, hot flashes, and sometimes nasuea. This lasts for about one hour and then I'm completely back to normal. Since I learned I have high bp, I thought maybe it was really high... so, I've checked it on three different occasions, and my bp drops when I have these symptoms. The worst was 111/58, and the other two times it has been around 112/60, which isnt bad, but quite a sudden drop from what it usually is, especially the bottom #. I watch the bp numbers drop as the symptoms get worse, and rise as I start feeling better, so there is definately a connection. So what I'm asking is what can be causing these symptoms and the sudden drop in bp??????