Im still in love with him - but its over?

I broke up with my partner of 4 years in February and am as heartbroken now as I was then. I can't eat, I hear him moving around the flat, I dream about him, everything reminds me of him, my thoughts are always on him . . . my whole life has come to a standstill. Ive been signed off work with depression and anxiety. I wake up having a panic attack every day and i panic when I leave the house in case I see him with his new girlfriend. Ive taken all the advice I can, i force myself through each day trying to see friends, keep busy and move on with my life but I still feel dreadful. I ended it for some very good reasons and I still stand by those reasons, hes still behaving exactly the way he did before the split now. It doenst matter how much I try to battle my emotions with my rationale for ending the relationship I can't let him go. This new unfamiliar lonely life I find myself in is too much to bear. I feel very alone, even though my friends are exceptionally patient and supportive. I feel frightened and can't imagine a future without him. I really love him and always thought we would be together forever, I wanted to marry him and have his children and never anticipated being single again. I can't even contemplate meeting someone else I had found the one I wanted and as a result of unlucky circumstances hes gone forever. Ive had mental health support, im going for counselling, ive read self help books and constantly browse the internet for advice but to no avail. Does anyone have any insight into how I can move on from this?