I am insanely addicted to porn and masturbation, it's effecting my mental health. how do i fix myself?

Seek support: You need to talk to someone, your doctor, perhaps a therapist that specializes in sex addictions. Medications may be of some moderate benefit as well, ex ssri's, but used alone would unlikely take care of the whole problem, there are 12 step meetings for sex addictions as well such as ssa, sex addicts anonymous. You not alone.

Support manditory: You can't fix yourself but you can align yourself with people who can support you in your recovery. In addition to the fine groups already listed, i would highly suggest that you seek out your local celebrate recovery chapter and see if they don't have a group specific to sex addition. You've taken the first step by admitting you need help. Now let others help you down the road.