Hi Imnotalone,
good name, good reminder that you're not.
It sounds like you're taking your own mental health seriously and that is a really good thing. When you feel low, that's the time to both accept that the lows will happen and that they will pass. It's hard to go through the cycles, but they do get less intense and less frequent.
If it often happens as you are falling asleep, is there something specific you can do for yourself at that time? Breathe / Meditate? Listen to calming music? Some slow stretches before you get into bed? Reading here and reminding yourself that you are doing something positive for yourself is really good. Eventually you'll be able to give yourself that peace.
As for the memories and sadness that creeps up - I think many of us hear you on that. For some reason (I'm trying to figure it out) I have missed my ex so much the last couple of days. And I consider myself to have made a lot of progress. But I recognize that it will take a while, because at least some of my sadness and regret is with how much better I could have been in the relationship. I do miss things, but I know that it's ok to feel sad sometimes. Sadness about a specific thing is much better than constant anxiety or general sadness / depression about my whole life!
Do protect yourself, as you are doing, by
not looking at her social media. Even if nothing were to be seen there, you know that you are not looking because you do not want to look back - you want to keep moving forward. That's the best reason to not look.
Keep talking to us. That's a better use of your time.