Well you've posted in the New Year thread instead of starting your own, but doesn't really matter
These things are always really hard to start talking about, but it gets easier with practice. I held everything in for years and now I think I talk too much.
Maybe the memory loss itself it traumatic to you because it was a frightening experience, it could be that something happened, but also not. I think if you were seeing a therapist it would be a great thing to talk to them about because they would know whether it was wise to explore this or whether you needed some tools to start letting it go.
It sounds to me like it may have triggered a period of depression one way or another.
I am sorry to hear about your nan. If you are still grieving now that is already hard enough.. but if coming back home in a hard time was a secure thing for you then you will be feeling this loss even harder. No wonder you are scared to lose more, you are trying hard to hang onto security and that is completely normal when feeling low.
Maybe you can just print these posts out and take them to a doctor, then you don't have to think about what to say anymore. It will take the pressure off you. I think if it has been two years now it would be a good idea to go to the doctor, because it doesn't seem like something that will get better easily without support.
Let us know how it goes if you go, if you can't face it yet then you can at least keep talking to us. But then maybe you can start a new thread for yourself