Is this sexual assault????Please help!!!?

soo there is this guy and he is always staring at my chest (i am 13 he is 14) and i think nothing of it because i am like in love with him and we r good friends (and he is soo cute!!!)but yesturday when i was putting my phone in my pocket he walked over and was looking down my shirt right there probably thought i didnt even notice but like now every time i think about him i get weird goosebumps and my stoumach hurts and idk if it is because i like him or because he did that to me and also wondering if that is assult to walk up to someone and look down their shirt PLEASE HELP!!!!