yea, no worries! it seems your at the begining stages. welcome to the wonderful world of puberty! dont worry about your size now, it will get bigger... but everyone is different at the start so its hard to say if your "normal" because there is no "normal" in puberty. everyone is different! just be happy with yourself. about the cum... hmmmmmmm
my guess is you just are the horniest during the day. but really, i dont know. i know when i was just starting, being in school was the easiest place for me to be aroused with all the cute guys and girls around (im bi).
do you think you know your sexual preference? no worries if you dont, it may change anyways... who knows!