Hi OP, didn't want to read and run but wanted to at least share a few words and my empathy.
I was (sort of still am - I posted just the other day about it) in your position too. Break up after 6 years and whilst I had some answers as to why, there are so many comments that make me think 'what if' and 'maybe' and open up more unanswered questions.
It hurts like a bitch and life is hard to function, however I agree with others that it does sound like a trip to the doctors may be a sensible answer, at least for the short term. It will just help take the edge off your emotions and help to break the cycle. There is absolutely nothing wrong with needing a little support (I have taken the counselling route).
Believe the other posters and me when we say the best thing you can do is cut absolutely all contact.
He will not offer you any relief from your pain and emotions, contact will only add to your confusion and prolong the heartache as you cling to any minute flicker of false hope.
Use this as an opportunity to put yourself first and to invest in a little 'you' time. It is hard to drag yourself up and out of bed (god I know how sometimes you barely want to move), but you need to keep yourself busy and distracted and remember what else you love about life. See friends (even if for a few minutes), spend time in the gym (20 minutes is better than none!), spend time with family, take comfort in the little things, and the people around you. See anything you do for yourself, and to put yourself first as a mini triumph to getting yourself back on track.
You know what also really helped me, just to even begin contemplating the process of moving on? A written list of all of his faults, and why I was not happy, why it didn't work out, and why I would be better off without him. It won't make everything go away, but it may just help you take off the rose tinted glasses (we have all been there - me included).
I hope you are feeling better soon.