What should i do about my ex boyfriend who is haring me?

My ex and i dated for nine months. I never told my parents about us. We are both 15. We broke up, and now i am dating someone new. My ex sends me texts constantly about how i am a , how i broke his heart, how I never actually loved him. Calls me a liar too. He texts my bestfriend about it as well. After about a week of this, he apologizes and says he wants to be friends. Then the cycle starts back up again and I recieve more and more messages.He threatens to hurt my boyfriend. He egged my boyfriends house, and on the same night, called my exactly 17 times all around 3 am. When he texts me in a friendly way, i text back in a nice way, When he calls my names, I try to calm him down. but i never retaliate with names. He is currently threatening to come to my house and drop off a provacative present (that me and my friends gave him as a joke). When he told me that, and whenever he says rude things, i dont normally reply, and the essages get worst and worst the longer i dont reply. What do i do?! This is serious, but i cannot get my parents involved because they did not know about this boyfriend, and it would ruin the trust i have with them about my current boyfriend. Plee help me I am really scared and nervous and I just want it to stop! What will get through to someone like him?!