I am going through the exact same thing right now. It is hard, i still dream, think about and miss my ex. The night i found out she was seeing someone else was the most gutting expirience. I didnt eat or sleep for days. I think the best thing for me was just time to feel it all and let it run its course. I still have feeling for her 4 months later but i have been dating even if im not into the other people i still date and it does help me feel better about getting out and about. The lonely part does suck but i think its a cruicual part of the progress to be alone. Im only just starting to be comfortable and happy with myself which has taken time. Things that helped me were just taking to mates and concentrating on my job which in turn kept me busy and a little distracted. I dont txt or message her and i have told her i wont until im ready which has helped ALOT in regards to her with her new partner for me. If you have friends who have been through this its always helpful to discuss and talk to them about it as they might shed some light on the recovery process or even just being someone to vent to. I think either way they will move on and find others and the only way to move on is accept which sucks. Im beginning to realise that now 4 months later. I hope this helps.. your not the only one who feels this way which is nice to know… i hope you start feeling better soon.

Its so cliche but its true time does heal..