Getting over a separation

I recently left my partner of 5 years because I never felt valued and felt like he took me for granted. He worked 4 nights a week and went out on his own three other 3. I have found out he is seeing someone and I feel like my heart has been ripped out. I can't get over it particularly as it is someone with very loose morals and in his words to me before he started seeing her ' a complete slag ' Why I keep asking myself he never liked her before absolutely hated her and I can't get over it. He takes her out for meals and takes her out every weekend. Why didn't he do this with me? I am absolutely gutted feel sick and anxious all the time and can't stop thinking about him. I can't concentrate on anything and all everybody says is I'm better off without him. It doesn't feel this way at all I feel like I'm just waiting. I didn't leave because I didn't love him I left because of how he treated me. I just want him back and want to go home. Does anyone have any help for me it just all seems so hopeless and pointless