My arm tendons ad elbow hurt?

whenever I kinda put my hand back , kinda like if I wanted to put my palm and finger tips to a ceiling it hurts. or when I snap. also when I make a fist it hurts, it all hurt like my tendons in my forearm. and my elbow hurts when i do certain things. and my bicept. so pretty much my whole arm hurts. I don't know why. it's been hurting for a couple days. I pitch for high school baseball. if that has anything to do with it. what wrong with my arm? please help. thank you.