In truth, I think the only thing you can do, hard as it is, is to get on with your life as best you can... I found that these things, if they are going to repair themselves, are more likely to do so when you aren't focussing on them. An oddity of life. Offering you promises that things will get better would be no good as no one can know if you two will get back together or not. It is good that you are giving him space, but the best thing you can do is to write him a letter expressing your feelings (if you have an address and haven't done this already) and try and come to some peace with the possibility he might not come back to you.
If you have any friends at all, try and spend some time with them maybe...if you have a hobby you have neglected, try and get focussed on that. Do what you can to keep your mind off him or you will just drive yourself nuts.
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I am diagnosed as a human being.