Am i doing something wrong ?

ARGO: I would have to say your pretty much on par with most heavies but if you want to improve your odds, don't let your self beleive that your heavies invulnerable. Use "peek A boo" and "pot shot" tactics as well as sniping to last longer. I have tier 9 and 10 tanks and I have been known to play sniper with them because it can confuse the enemy into thinking I am a TD and wondering a little to close. Train your crew to 100%, get a camo net, and you may consider a tool box and or verticle stabilizer to give your heavy better chances of hanging in a dog fight longer.
Or simply watch how other play and adapt it to your own style.