So I’ve always struggled with food and my weight and always been told either that’s just my body or I’m “just a teenager” (I’m 20 now)

I always describe my relationship with food as I know I’m really underweight, I want to put on weight and I need to eat and I will eat but I don’t at the same time I hate the image I picture when I see myself weighing passed 8 stone or if I eat a lot in the day I regret it , if I have a meal in front of me I feel sick or my first thought is I can’t do that, and it takes me a while to me hungry and barely any time to get full. Oh and I sometimes go through phases of eating more than normal for about a week and then go straight back to the normal feels and routine ( but that’s normally around my period)

So in short I know I need to eat and put on weight and I want to but I won’t and I don’t want to at the same time

Normal or should I be heading to the doctors idk I’ve never wanting to think that it’s possibly bad but idk just thought I’d ask some strangers there opinions aha