I can't really pin down why I get jealous. I just get intensely jealous and I know I care for someone because I go from not caring about what they do to the next day feeling like killing myself over them liking a photo on facebook.
i feel like i can physically feel it when it happens. the mix of rage, sadness and jealousy literally burns in my head, kind of like a headache probably from the stress and trying to hold in the tears