I found the word やめたくなったら. I think it's a conditional past form of やめる. Or maybe it's やめた conjugated with なったら (conditional form of なる). But the く in the middle distracts me: I can't find this form in a dictionary. Can you help me to find some grammar for that? And all I can guess for translation is only like "if want to stop".
やめたく is not the た-form, it is based on やめたい ('I want to stop'). なる requires a construction either with に (for nouns and な-adjectives) or -く (the adverb based on い-adjectives).