Well it's ony because it's got sugar on it. You are basically eating like candy- sugary cereal straight from the box is so good- but if it says cereal you think of oats and wholewheat and so you think it's healthy. It isn't really.
I mean if the cereal was shredded wheat, or bite size shredded wheat NOT the fristed kind, Im sure you wouldn't eat so much, or if it was plain oats.
But no, you're eating the High Fructose Corn Syrup kind of cereal- it isn't even good quality wth sugar in it. There may be sugar in it, but only after HFCS and Corn Syrup and three different types of sugar.
When I was little I used to LOVE eating Sugar Puffs from the box they are like "Honey Puffs" or whatever that puffed wheat cereal is, with honey and sugar, the minute you pour milk on it, it's soggy, so I LOVED it plain from the box. But at least that was just sugar, and not HFCS.
Can you ask your family to eat shredded wheat or oatmeal instead? They are the only plain cereals which have only one ingredient each.
There are ther cereals which you might like to eat once a day for brekky, but not out of the box- all bran, bran buds, grape nuts.
If your family don't want to do that, ask your mother or whoever buys it to buy the cereals without sugar, because sugary HFCS and Corn Syrup cereals are SO BAD for you anyway, you may as well eat sweets and chcoclate.
If she says no, then basically stop eating that cereal- only eat whatever YOU buy yourself. You aren't even paying for it. At some point you'll leave home where all your stuff is bought for you. If I had a kid who ate things like you do, I would lock the food up and tell them they can only eat that way if they buy it themself- that will be a good way for you to stop.
Will power os all very well, but hard if you have nothing to stop you.