Which leads me to conclude that, there must be some sending address (just like your own paypal email you use to send $$$) - which must be how they know that this is the same person who rolled first and the second time.
SO the question - HOW CAN I CHANGE THE SENDING ADDRESS OF MY WALLET every time I bet(if thats possible)?
Your conclusion is wrong. No identifying information is sent in a transaction. They probably know it is you by giving you a unique address to send to. If somebody else sent money to that address, they would still think it was you that sent it.