I live in a (for me) very stressful house, where i have a negative association with. i've been taking gabapentin to sleep at night. lately, it seems to have stopped working completely (won't relax my legs), why is this?

Not surprising that you have developed tolerance. Real question is whether you possess Restless Leg Syndrome, and if so, a dopamine agonist is the best choice. Find a neurologist for this. But for stress, find a counselor or psychologist and address potential solutions or intervention. Fixing but one problem is likely insufficient to stabilize fully.