How do i stop her from being jealous.?

well me and my girl have been together for over a yr and since then her jealousness has grown worse and worse. she gets jealous if i go to my own familys house. i use to weigh over three hundred pounds and lost all my weight. she says im doing it to find a better girl. i pay beyond attention to her and it dont seem to be enough. iver never cheated on her or lied to her. idk where the jealous comes from. she has never been cheated on either or did wrong. what should i do. im half tempted to call it quits. ive lost all my friends cause she dont want me anywhere but with her.