Being home might just be a trigger. Subconsciously, your brain connects being at home with masturbating so you feel an urge when you go home.
I get this when I go to certain places, hear certain noises and the like that I associate with masturbating. It could be, but it doesn't have to be for any deep reason. here is where "urge management" (I just made that up) comes into play. Things like urge surfing or distracting yourself and making sure to keep productive are the way to go.
Of course, there can be other things at play like anxiety or some other emotion that we may feel when we are in specific places. I have some negative associations with my parents home and sometimes when I visit I can get very tense.
I think the trick is to be really aware and really honest. Don't overcomplicate your feelings and desires. There is nothing wrong with the desire to masturbate or watch porn, that just how you are wired. If you desire it, let it be just desire, it doesn't have to be some deep yearning for "connection with Hashem" that's manifesting in the form of watching sex on a screen. It could be from negative emotions, or just plain taiva, or both, all of which are normal.
It's not noble, it never was and you know that it's not. You may want to accomplish, then feel bad for not accomplishing that thing, but no one can convince themselves that masturbating is "noble."
You made a plan for when you are home, did you include goals, positive things to accomplish over the next week? This might be the most important of all. Make sure to make it realistic though. Some goals in davening (like davening before the zman), some goals in learning (at least 20 minutes, in the morning), some goals in helping out at home (doing errands for your mother) , and some projects that you always wanted to do.
