Ally I too felt like this when I had to leave my little girl. It is gut wrenching.
We decided to bring our baby girls ashes home. I felt such peace when she was finally home with us again. It really helps me.
I also light a special candle when I am really missing my little girl - it's my sign to her that I am thinking of her and love her.
I find it hard to know what to say because I don't want to upset you or say anything wrong and I certainly am not trying to hijack your thread I just thought by sharing some things I have done might help you and maybe you could do these things too maybe it might bring you a little bit of peace but maybe not, we are all different and cope differently there's no right or wrong. I am so sorry for your loss. You have loved your little boy so much, you have taken such wonderful care of him and are such a wonderful worthy mum - You haven't left him honey because he is forever in your heart and I am so sure he is with you in spirit right now.
Take care of yourself xx