please help.

For the last month for some reason i used to also do it some times but mainly this month i have been going to sleep and waking up completely tired out.
my brother has said hes seen me walking down and stairs and turning on every light in the house then turning on the pc, ive also found myself in weird places such as dressed in my school uniform crashed on the floor on a sunday morning. ive also walked straight out of the house onto the main road and down to the church where i catch my bus for school.
whats worse is i don't wear nighty's to bed very often and i cna be naked and walking around the hosue doing all kinds of weird things.
last year my parents thought i was self harming cause i woke up with bruises and scratches all over me very often, though i do have very odd dreams and can be heard crying screaming out hitting walls kicking walls and singing, i talk regularly in my sleep but it there a way to prevent what has caused me to be sleep walking so recently as i don't want to hurt anyone.