Replying to Renters help

First some basic info I rent in denver. I left for 3 days to go visit my family in Cali and I just got back and I have alot of water damage in my. It ruined my brand new mattress and it reaks of mold in their.

Now it has had small damage before when there was a big rain and I had called right away. A few days later he sends over his contracter and the guy says that there is no problem and that he cant explain how water got into my room.

Now can anyone help me with what I can do. I really dont want to have to pay to replace my brand new mattress and anything else that got messed up?