Health Monitoring Software / Diary?

At the moment, I find that a) I am getting a lot of minor illnesses and b) I often seem to get adverse reactions to food. I’d like to investigate both these situations a bit more scientifically that I have to date. Is anyone aware of any software / products out there that help me do this? For example health diaries etc, that allow you to record / monitor the state of your health against external factors such as diet etc?
Basically, I would like to monitor the state of my health and be able to correlate it against certain factors. For example – diet (to highlight any allergies), stress at work, level of exercise and so on. Can anyone help?