Being male with 5 children, I have had some experience in this area. First let me say two things. 1) I am reluctant to get too explicit because it can be an occasion of sin. 2) The level of questions you are asking depend so much on the individual that there are not dogmatic answers. So here’s my best shot at answers.
Having an E is not M. M involves a self-sustaining activity which usually ends rather… definitely.
The church teaches that M is a grave misuse of our faculties - mortal sin territory, so confess it if you have problems. M can become a bad habit or compulsive, but with God’s grace, it can be overcome.
The psychology and physiology of males is such that things will pop up given the appropriate stimulus (which you may have no control over). This is not sinful. However, arranging to get the appropriate stimulus (porn, TV, fantasization) is sinful. Taking pleasure in these thoughts, even if they don’t lead to M, is sinful.
So don’t get hung up on that.
Lastly, don’t always try to attack these issues head on. The more you focus on them, the stronger temptations can become. Concentrate on your school work, exercise, serving others, and loving Christ.
There are a good number of resources here and elsewhere on this topic. See here pureloveclub.com/