Is stress making my hair fall out?

Im only 14 i always use to have thick hair but now it is so thin. This year im in 9th grade i take all accelerated and ap cles idk if maybe the stress is making my hair fall out also in the past year i have lost 85 pounds. idk if maybe im mal nutrient would that cause this? also i have these dark spots that almost Look like skin pigment fading or like liver spots on my collar bone. I don't know what to do i sometimes just come in my room and cry because I don't know what to do.