I’m so sorry you went through such a turbulent time in 2020 both within yourself and your relationship, but the first thing I noticed from reading this was just how strong, kind and caring you really are. It’s definitely easy to feel blame or guilt when we have to make difficult decisions, but I just want to begin by saying you are truly so compassionate, introspective and empathetic and this really shows.
I’ve been in a similar situation however the other way around, as my mental health, unfortunately, lead to a recent break up so I feel I have some insight into the situation you find yourself in. I really struggled to accept the decision myself, but the circumstances were different, and in your case, I really respect the time, care and patience you have given to your ex who is so lucky to have someone like you in their life, period. Although it’s easy to focus on his mental health as the main factor in his efforts and current state of mind, I think it’s important to consider that maybe these factors would have led you to the same decision regardless of his commitment to making sure you’re fulfilled in the relationship. You highlighted that you have different priorities in the ways you spend your time, socialise and be around others, and I think this might have caused problems in the future even if he was feeling like his best self. Breakups are always difficult but they can feel even more challenging when there isn’t a major reason behind them, so although he didn’t explicitly do anything ‘wrong’, it’s not to say the relationship was right for you at this point in your life.
4 years is a super long time to spend with someone so please remember to show some kindness and patience for yourself too, as it’s all well and good being concerned about him but you have to look after number one too! Despite his mental health struggles, it does sound like he took the relationship for granted somewhat and over time that has of course caused you to doubt your security with him. No matter the circumstances you should always feel like you are wanted and valued in your relationship and it just seems like pandemic aside, those were not emotions you felt with him.
It’s natural to feel an obligation and desire to keep supporting him and be an ear to listen when he feels he has no one else to turn to, but know that this isn’t your ‘job’ so to speak. He may find it difficult to speak to others, but it’s not healthy to place so much of his emotional baggage on to you and you alone. Perhaps you can hold his hand a little in lightening the load, maybe by looking into therapists that seem like the right fit for him or getting advice from a mental health charity on his behalf- it will help you to feel less like the weight of his MH is completely on your shoulders, and hopefully aid in supporting him too.
It’s a really difficult situation and you’re handling it so maturely and compassionately so like I said make sure to prioritise yourself and your emotional needs too. Lots of love, you got this!