The fact that you were able to stay clean for over 100 days and put such a distance between yourself and the addiction, this is very powerful. With this knowlege, you will never be able to go back to your old self again. Also the fact that you didn't go all the way even when you fell, shows you have great inner strength!
Don't let the fall of the past week get you down. You haven't slid back to first base, you are still just where you were before. Only you have to get up, brush yourself off and continue the journey. Sometimes heaven makes a person fall so that they should get back up and become even stronger than before.
I don't know if pre-cum is as serious as real semen. I don't think it contains actual sperm cells but I am not an Halachic authority. In any event, this is besides the point. It is the 'porn watching' which is the root of the problem, and it is those types of behaviors that are truly addictive and dangerous to your soul. Also, bringing oneself to an erection intentionally is seen as very serious in the eyes of our Sages.
But it does not matter anymore. The
you of yesterday is not the
you of today. What was, was. Jewish philosophy and Chassidus teach that a Jew has to look at the past and future as out of their hands. Whatever was already, G-d wanted to happen. Only the present is in our hands. For more explanation on this seemingly strange concept, see
here.
To make sure you don't fall again, try to learn to guard your eyes everywhere you go. Not just on-line, but even in the street.
Shmiras Ainayim can take
years to perfect, so be patient. Every time you turn away from something bad, it is like you are putting a coin in the box. Even if you fail many more times that day, that coin remains. When the box is full you will have perfected your
Shmiras ainayim. And I can't tell you what great reward awaits those few, select people on this world today who have overcome this great battle. You will be worthy to behold the
Shechina when
Moshiach comes and in the next world!
Keep posting your progress on this forum so we can give you encouragement and be encouraged as well