How do i tell my EX to stop? i already have a boyfriend!?

My ex-bf keeps trying to get back with me. he tells me he wants to **** me & he will always try to hold my hand & tells me im pretty & he likes me & get really close to me & asks me out even though i keep rejecting him. he flirts alot even tho i dont flirt back. when we give our goodbye bugs to all our friends in the end of the day...he gives me the longest hugs. we hang out with the same group of people. i have more groups but thats the group of friends i hang out with at home at my appartments. ive told him to stop. but i think he thinks i dont mean it. im 14 and going to 9th grade & hes 15 & going to 10th grade. i have a boyfriend! my boyfriend doesnt know we went out before he thinks we r just friends. my bf is also 15 & going to 10th grade.....my bf is the jelouse type so i dont wanna tell him cause he told me if any guy trys to hit on me he'll punch them in the face (he will & hes strong). so i want to solve it without letting him know. how do i get him to stop & for us to just continue being friends?