I’m so sorry to read that you’re feeling so desperate. It sounds like you have been through a very rough time after having your little boy and it sounds like you need post natal support and counselling, first and foremost. The codeine use is a symptom of that. There are some small steps you can take to move forward. A drugs & alcohol team, your GP and birth trauma specialists, I’ve mentioned all these below.
Becoming a parent is one of the most life changing and challenging things that can happen to us even with a healthy child. To me as an outsider it sounds like you have an infinite amount of love for your son and that is why you haven’t cared for yourself, that’s nothing to be ashamed of, that’s you trying to cope and putting him and worrying about him first before everything else. As for breast feeding, that’s a totally normal way to feel, 11 weeks is an achievement and once you’re in a more positive frame of mind, you’ll realise that.
The first thing you need to do is find a drugs and alcohol service in your area and ask them for support. Most of them are easy to find on google and phone to get an appointment. They’ve seen it all and are non-judgmental, they also don’t force you into anything you’re not ready for.
Are you on antidepressants (or ssri’s) as they are known? If not, you could talk to a GP about that. There are also specific counsellors now who discuss traumatic births with women who have suffered them. The maternity ward/ health visitor or midwife will be able to give you a number or search online for your area.
There are definitely a lot of small steps you can take. There are reasons you have reached this point and none of them are anything to be ashamed of. Well done for reaching out on here x