Healthier body

I have always battled with my weight... Everyone always complains about being overweight but I'm the opposite.... I'm not under according to the charts but to me I look it and to others (at times, family) say it. I eat like a cow (maybe not as healthy as I should) and stay active with my three kids and excersize here and there. I know protein shakes and all of that would help but I hate them and have yet to find anything else. How can I gain weight to feel and look healthier to me???