Pretty much everything needed has been covered in this thread...
If you are still aware of ex and her new boyfriends activities with her, then you haven't followed the whole 'no contact'.
It's an horrific thing to go through but you must completely forget about her, delete everything, no contact, no stalking, no looking up her friends etc.
Time is a shite healer imo but all you can do is learn from your mistakes and don't make them with the next one.
Of course she was all nice and telling you she doesn't love him, she did that so not to directly hurt you in person, her guilt or feeling sorry for you out of old love would of made her romantically connect with you, even if for only a few minutes. It was fake, you need to accept she's moved on.
It's seems difficult now as your head is probably running through thousands of scenarios, replaying all that happened with different endings etc, 4 years is a long time but you just need to give yourself some space to heal and get used to a different way of life, then once you replace her you'll wonder what all the fuss was about.