Am I overweight for my height and age?

Am I overweight? Okay, I weigh 145 lbs, and im 5'6. I'm 14 going on 15. And why does my weight change so much? I'm hypoglycemic and sometimes I follow the diet but most of the time I don't, so I think that might be why it changes. Like, two days ago I weighed myself and it said 150, now it says 145 and this morning it said 143 lbs. I'm confused, and I can't go off of what the doctor says cause the last time I was weighed was about 4 or 5 months ago, and I left my shoes on (converses add about 4 lbs) why is it so jacked up? I work out everyday, so it isn't cause some days im burning calories and others im not, please help!