Have gained 50 lbs in college. Help

Ok I️ know this is insane but there is definitely something wrong with my metabolism. I️ am a healthy eater (was a nutrition major but changed because I️ was embarrassed being overweight in the major) workout regularly and am an overall healthy person. My twin on the other hand eats incredibly poorly and maybe has worked out 10x MAYBE in these past few years and has been between 10-20lbs.

I️ think I am going to get my blood work done because this is just getting out of hand. I️ am also worried because I️ don’t want it to be PCOS but I️ only have severe cramps through the whole month and rapid weight gain as symptoms. I️ used to drink a lot but not enough to gain 50 fuckin lbs esp with a balanced diet and exercise. I’m also on the water polo team which adds to the exercise aspect as well. HELP!!!! Please give me some insight

Oh also I’m a junior