My ex boyfriend

So me and my xboyfriend broke up not so long ago and he already has another girlfriend. I cant stop thinking about him. Seeing him with her is just breaking my heart. I've told him I still love him. But he says I need to get over him. But I cant. We have been through so much together and I just cant stop loving him. But the worst thing about it is his sister is my bestfriend so im always round his house and have to see them flirting. I dont want to move on I just want him back.

Please help what can I do?

Desperation is very unflattering. You really should get a life that you enjoy without him in it. Find things that make you happy, and move beyond the pining for an ex. It takes time, but it will get better if you keep yourself busy making yourself happy. We have all gone thru this and learned to move on. He has moved on, you should to!