au0, you've had a really rough start with your baby and you've worked so very hard to feed him. I'm sorry things haven't worked out for you this time - I can see this was important to you from all the preparation you've done and work you've put into it. You have breastfed - maybe not as much or as long you you intended - but I hope you can feel good about what you have done. Every drop is important and worthwhile. Sometimes, despite our best efforts, circumstances around us mean we can't achieve what we set out to.
If you want to give the ABA helpline a call, or even drop in to a local group meeting, one of the breastfeeding counsellors will be able to talk you through your experiences and help you with the debriefing and grieving process. Some mums find that helpful.
From a practical perspective, I will echo Onyx's suggestion to stop slowly, to reduce the likelihood of painful blockages.