What to do?

Okay, it's been a long time since a last posted a post. As i said, this is the place for me to express feelings with no boundaries. Well, she told me she still loves me even after we broke up. But she doesn't to fine back? that's weird but it's okay i guess. i've tried to ignore her for whole day but somehow, either i will message her myself or she will message me. I constantly ask myself, what's my feelings on her now? My mind is getting more and more confused as the days go by. I do not know what to do right now. I've tried literally everything. I've tried the silent treatment, I've tried to be cold to her just like what she has asked me to, I've tried the caring method. But, none of them is working. Maybe she's just lying to me? Maybe she's just feeling guilty? Another thing is, i felt that she's constantly jealous about everything. Even my long lost ex? Erm, her jealousy also showed me her feelings towards me i guess. She's been talking about the key to her heart since the day we broke up, so here's the situation. There's another guy from PFS, currently 18 or 19 I'm not sure who is chasing her too. I felt that he's a big threat. He always asks her out with him. Which worries me a lot. He's always messaging her. More then i do sometimes even when we're together. She refuses to tell him about our relationship? Or maybe she's cheating on me? Nah, i don't think she will do that. She's not that kind of a person. Haiz, what to do?