It is possible, though probably unlikely. Anyone can get diabetes at any age, and although it does run in families it does also sometimes affect people with no family history. What are your symptoms? An awful lot of 15 year olds are constantly hungry, and most of them aren't diabetic! The classic tell-tale symptom is excessive thirst (if you get very thirsty and both drink and urinate more than you used to - that is suspicious). Also, tiredness for no good reason and sudden weight loss - again for no obvious reason are common symptoms. There are others, but those are likely to be the ones that are most apparent.
If you think you have any of these symptoms then go and see your doctor. He or she can tell with a simple blood test, and it will put your mind at rest (also if you do have diabetes then it is better to find out as soon as possible, so you can start managing it before it damages you). However, if your main symptom is hunger, then that is probably just being 15!
As for your diet, I'm certainly not going to get preachy on you. Assuming that you aren't either diabetic or massively overweight I wouldn't worry too much - it won't do you any good to become obsessed with your diet (that way lies all sorts of horrible socio-psychological hangups!). Yes, it is important to teach yourself to eat healthily but it isn't something that happens overnight - and being aware of the issues is half the battle. There is nothing wrong with sweet food, just try to eat it in moderation and alternate the junk with fruit and vegetables. If you don't often cook, then try learning to do so. It is actually quite good fun, you will end up eating nicer and healthier food. When you do cook, try to use actual fresh ingredients rather than pre-packaged stuff. Also get good quality ingredients (e.g. vegetables from a greengrocer, or even better a farm shop, rather than a supermarket) - again they will taste better as well as being better for you.
. My mum said that it was probably just my age but i wanted to see what everyone else thought because she's used to me worrying about my health. The littlest abnormalty catches my attention and i worry about it for ages. You've put my mind at rest. Once again thanks. I've decided to cut down on snacks so that i get into a normal routine and see how that goes. xxx