You seem to be going through a tough time. Yes, it can be very difficult after a break up especially if you were about to get married. You had seen many dreams, invested so much time and emotions into your special relationship. Feeling anxious and not able to see the future clearly are related. If people are holding you responsible for the breakup, is there any truth in this? Regarding guilt, take on only that much responsibility for the breakup which was caused because of your choices. You might be thinking that you will never be able to find another man like him.
Next Steps
See a counselling psychologist to help you decide what you want to do next, manage anxiety and sleep better.
Health Tips
With high emotional turmoil, its hard to think clearly. Sometimes, the future is not clear anyways and you might have to still take some action. I suggest that you give yourself some time, don't take any pressure and not take any hasty decisions yet.