Having Unexplainable Marks That Look Like Burn Marks All Over Body. What Could They Be?

so. i have un explainable burn marks all over my body. most have scarred now. one on my left elbow/ arm . one on the back of my neck , lower back, inside of left foot , and leg , otherside of left leg, both thighs and a new one after months of not coming up has just came up on my inner ankle on my left leg. This has been happening over the last 4months and iv e spent a total of 4 weeks in hospital because of it and my parents have given up on taking me to the hospital because they do not and can t figure out why it is happening so they referred me to a physiological department thinking im self harming myself. i must admit, i know what a burn mark looks like and they look exactly like them but are not. Everyone has given up on finding out what they are but it is excruciating and i need answers. Can somebody help me?