Hi I am a 13 year old girl and I am very fit and healthy but recently I have been having unexplained bruising on my arms and all down my spine. There are six in all, 3 on my spine, right on the bones, 1 a little more towards my hips, 1 on my left forearm and 1 on my right upper arm. The bruise on my left forearm was bright red up until this morning, which was when I noticed the spinal bruising. I know for a fact that I have not knocked or bump into anything.