What Are The Long Term Effects Of Blood Transfusion?

Hello, I would like to know what the long term effects of a blood transfusion are. I had to have an emergency blood transfusion during a miscarriage where I lost approx. 4 L of blood. This took place 2 years ago and ever since then I have been sickly. My body does not feel as healthy as I once was even though I work out and have never been over weight, am a non smoker, drink very little and not often. I am 37 and a mother of 4 healthy children. I work in education in an elemntary school and it seems that every sickness that runs through the school I always fall ill to. I have already taken all of my sick days and we are just over half way through the year. I also had an emegency stomach surgery in 2001 due to a perforated duodenum . Today, once again I am home from work sick with nausea , body aches and headache . I am sick of being sick and afraid that I may lose my job. I want nothing more than to be healthy. I hope you can offerme some feedback as to what has happened to my health. Thank you.