Hope? Advice appreciated.

I've browsed around here for a month now, and I've learned that every story is different and wanted to finally give mine, and get some input/advice.

My bf of 2.5 years broke up with me a month ago. We are both 20. Absolutely wonderful and loving relationship.

About mid April, I noticed he was texting a 17 year old girl a lot. He didn't try to hide it from me. But, it began to concern me. When I confronted him about it he told me he'd slow down the talking. I found texts to her that were flirty and I got upset. From then on he would tell me a few lies pertaining her, which I found out. We fought many times throughout May because I was very hurt and worried he had feelings for her. He constantly insisted that it was nothing but a girl who shared his interests (she's kind of a bro.) who he enjoyed talking to. We had one more fight one night and he had had enough. He broke up with me, and told me he couldn't stand to hurt me anymore, and couldn't stand that I was unable to trust him. Also, I was another stress added to his life.

I never begged, I just agreed. A week later I find out he is hanging out with the girl a lot and they have feelings for each other. We texted all day about it and he finally came by my house to discuss it. He explained to me that he did like her, but still had feelings for me. He said she was just a distraction, and a good friend. He also kept insisting that he may one day realize he is making a huge mistake and beg for me back. He said "I just need time." We were very intimate that day. He had to leave because I was going out dancing (which he very apparently was jealous about.) The moment he left I realized I was in a freaky love triangle with the person I have given my heart to for almost 3 years, and a 17 year old kid. I immediately removed myself from the situation and went no contact.

He texted me 5 days later, asking many questions "How are you? How have you been? What have you been up to? With who?" I was very short and he eventually ended the convo.

NC for 5 more days. Then he texted me when he saw on fbook that I was at a concert for one of our favorite bands. I didn't respond. Texted me again with a sad face. I didn't respond. He texted me 3 hours later in the middle of the night with "I miss my best friend." I still didn't respond, but was very relieved to know he was thinking of me.
He texted me the next night. I did not respond. He finally sent "So you're not talking to me?" Stupidly, I responded, which began a conversation that bled into the next day. He just wanted to be friends, and I told him I couldn't be his friend. He was very upset. I told him I had also lost respect for him for moving on to the next girl. He said "I haven't moved on, not in the least." And ranted on about how badly he didn't want to lose me and how hard he had tried to not let our relationship fail. He went on (again) to say that this girl was a distraction from him thinking about me. He tries to downplay her. But I know they are seeing each other and have feelings towards each other.

I ended the convo very angrily and told him I had learned to hate him in order to make it easier for me to let go. I think I upset him with this. I told him not to expect me to be his friend or talk to him.

It's been 2 weeks since that conversation with no contact (except him texting to ask if I had a shirt of his)

I miss him very much. How do you cope with your ex being with a new girl? What should I take of him insisting that I not lose hope in us? I am smart enough that I have been moving on with life without him. Talking to other people. Exploring new things. Becoming a better person. But he lingers in my mind.

I miss my best friend too. Is there hope?