Unexplained Health Issues: Seeking Answers

In March of last year we were coming home from vacation, where I had not felt well the whole time, and I got very light headed, started having what felt like palpitations, and chest pain. I went semi unconscious and my boyfriend rushed me to the ER. While there I found out my iron and B12 levels were severely low, and my blood count was 0.2 points away from needing a blood transfusion. Although I had not lost any blood what so ever. I saw my primary the next day, who referred me to an oncologist. I saw them and they ran a battery of test. I wound up having a colonoscopy and endoscopy and they found abnormalities in my colonoscopy but nothing concerning. I wound up getting put on a super vitamin basically, and having iron transfusions. A year later I still don't have an answer as to why? Why did all this happen? Why do I still have days where I can barely make it thru vacuuming my 5x7 rug without feeling like I ran a marathon? Then the last blood work I had done showed my blood count had dropped again. I asked the oncologist but he didn't seem concerned as of now. Any experiences with this? Why am I seeing an oncologist and not a hemotologist?