If you’re still living with your ex, move out, even if you have to sleep on someone’s sofa. It may sound selfish, but distance will give you the space to think about the situation clearly. Chatting to friends can definitely help, but it can be hard to discuss personal feelings, and they might not offer anything better than ‘there’s plenty more fish in the sea, mate’.
Don’t let anyone tell you how you should grieve. Find out what helps you. You may find comfort in activities like work, sport or hobbies.
Making a list of all the issues and feelings you have is a good idea – just seeing it all written down can make things feel more manageable. Try to look at events as they might appear to your ex and child, and think about how your behaviour seems to them. Be honest with yourself, admit blame where you are at fault, and try to make peace with your actions in the past. You can’t change what’s already happened, but you can change things for the future.