I'm so sorry to hear this, your head (and heart) must be reeling from all this news.
It sounds like decisions must be made fairly quickly on this, given that they are now telling you to stop all meds, which I'm sure have very painful implications for you.
One very positive thing is that they have said you can have a baby in the future, should you decide not to continue with this pregnancy. It seems to have happened at a very critical time in your recovery.
I'm not in any way trying to tell you what to do - you've through the mill, to put it mildly over the past few years. You need to do what is right for your family right now - for you, your partner and your precious ds.
Many of us here have faced very difficult decisions regarding much wanted pregnancies. Speaking totally for myself (obviously!) I focused on the people who were here with me right now, ie my husband and children and what their needs were, and indeed perhaps selfishly, what I felt able to cope with myself.
There are no easy answers here, only the way that is right for you, after all you have been through, your ds who must be a lively 4 year old
and your dp.
I know you will find a way through this, for all of you. x