I have no idea what to do

So I was dating this guy over the phone like video chat and texting and phone calls. Im 16 next month, he's 16 now. We went to elementary school together and for a while i was really feeling him. Well early on in the relationship he sent me a picture of... well you know. Ever since then my attraction towards him has been fading. Sometimes when i think about him, i think we can make things work but at the same time, when i think about him all i can see in my head is the picture he sent me. Should i just tell him why i dont like him anymore to get the stress off my back and then just be like friends or should i just block him on everything? I just want a clean slate on my dating canvas. PLEASE HELP!!