Can you get sick from too much sugar?

So, I'm a sixteen year old girl. I'me homeschooled and I'm quite behind so I've been staying at home a lot and I usually just make a gallon of (very) sweet tea. I've been doing it for about six or seven days now, and I drink about a half a gallon a day. I make the tea with 2 1/4 cups of sugar. I drink a glass first thing when I wake up, becasue I'm usually really thirsty when I first wake up, throughout the day, and before I go to bed and I have a glass beside my bed. I'm aware that this is probably not healthy; however, I've been really, just ill feeling lately. I can't go to sleep and when I do I sleep for thirteen or fourteen hours straight and I'm still exhausted when I get up. I can't concentrate on anything. I'm either further behind than I was because I keep loosing focus. I've had a near constant headache and my stomach feels like it's in knots or that I need to puke but I can't. I literally pee like every 5 to 10 minutes (though that could be that I drink a lot), and this one's kinda weird, but when I exercise I feel like I can't get enough air and my heart feels like it's beating out of my chest. Is this just too much sugar, or something else?