If I had unprotected sex 5 times in 3 days. And I was on my period, the chances are verry high of me being pregnant. What are the chances that I am not?

"Chances" apply to all women of childbearing age, and are meaningless when applied to one woman. If statistics says you have a 12% chance of getting pregnant while you are menstruating (a number I just pulled out of the air), that is a number that could be anything from 0% to say 25% for you, that month, that year of your life. Then there's the ability of the man's sperm to fertilize your egg. And so on!
Statistics are just this: let's say you fall into the low probability group for being pregnant. But what does that mean? It means you are 100% pregnant.