Well what jumps out at me is this ingrained feeling you have that masturbation is "bad."
You've had this for awhile bec you confessed it as a "sin", To a priest. I'm not sure what commandment was broken here.
Do you know? Why did you think this was bad? Who told you it was bad? Why all this guilt?
What has reinforced this guilt is the priests comment that you had to stop & its bad for you.

Now you're older. Think about why a priest would tell you this. There are many reasons, but do you agree with them.

I am a former Roman Catholic. I understand guilt from the church very very well. IMO it's used as a form of control, but I digress. If you can get over these feelings of guilt & shame of masturbating from what sounds like a religious point of view & maybe study this from a scientific point of view or any other point of view it might help with this tunnel vision.
Yes you need to look more deeply as to why you feel this way. IMO if you enjoy porn responsibility then enjoy it. Same goes for masturbation. Enjoy it!!