Tips on letting go of a past relationship? How to trust again?

It's been almost four months after i was dumped by my ex bf who cheated on me and there was other things that happened that left me feeling depressed and hurt my confidence. Such as lying to me all the time, knocking up his ex, and then dumping me after I lost my baby and he wasn't even there to support me when I had the miscarriage. It was traumatizing and all he said was sorry and he's moved on like nothing happened. it's been hard for me let go of the sadness and anger I have towards him but at the same time I still care for him even though I know I'm better off without him. I want to know how to finally let go and be ok with dating again sometime in the future and being able to trust men again?