Too much Soy?!?

Has consuming too much soy made anyone sick? When I first went vegan I basically lived off soy, and I became very ill to the point where I felt like I was dying. I was told I was lacking B12 and other vitamins in my system, even though I included them in my diet. Appariently too much soy inhibits the absobtion of vitamins and minerals in the digestive system. Has this happened to anyone else?