what is this massive bruise? could i have a deficiency in something? help!:(?!

so i am 15 years old and i am a vegetarian, i also get really dizzy every day, but i don't usually faint, maybe once every few weeks and it's never anything full on. anyway, i have this huge bruise on the inside of my thigh and it is actually darker than in the photo i took. (sorry the pic is really big, just a warning). anyway i was wondering if i could have some sort of blood issue like a deficiency in something cos i don't know how i got the bruise and it has been changing to a darker colour and it has gotten a bit bigger it just doesn't look like a normal bruise. i also have another big bruise on my knee (same leg) which i don't know the cause of, but that doesn't look as bad as this one. this one is about the size of a small egg maybe? a bit smaller, but yeah that's the shape. it might be nothing, but i do get dizzy. thanks guys.
pic: http://tinypic.com/view.php?pic=2il0kyq&…