Unsure what to do about my relationship and if his heart is in it/how to bring a spark back

sorry in advance because this is gonna be a fat rant/explanation! but I'm feeling anxious and unsure what to do 🙁

So I am a massive over-thinker which I always tell myself is just me creating unrealistic and bad scenarios which are super unlikely to occur. This obviously isn't the best trait to have in a relationship but I'm unsure how to stop it. Anyway, my boyfriend and I had been in a relationship for about 8 months, I thought everything was going as well as it could for someone who overthinks and I did not pick up any weird or different behaviours from him either to indicate otherwise. He had been going through a few weird circumstances at home around this time and he is someone who struggles to open up/communicate/let me in at times because he has always dealt with things alone. One day he came to my house with the intention to break up as he claimed he had within the past two weeks felt he had lost some feelings, but was unsure why and how and also still loved me. I was quite shocked as this was a total surprise for me and it did not feel at all as though this was were our relationship should end. By the end of the discussion he said he was 50/50 in making this decision and was clearly upset (crying, as was I) and hugging me, so we decided to give each other space for a few days and think it over. We met up and ended up getting back together, thinking of ways we could bring a spark back etc. but thats hard to do during coronavirus because we cant go out and do the things we usually would.

A week later and he was asking me to stay over quite frequently, things seemed to be back to how it was and he said he felt like progress had been made really well and we will make it work together. He also said thanks so much for giving us another chance, so all promising things. However, I just cannot get it out of my head that he's going to turn around and do the same thing again because it was so unexpected for me. Any little thing I will overthink and and spiral down into a really negative headspace and I do not know how to stop it, living with anxiety makes this harder. An example of me overthinking something stupid and minor is him being active on something but not responding to me until later.

I guess what I need advice on is if this relationship is redeemable and we can make it work (in the sense he could regain his feelings), how to stop overthinking any minor thing and how to get a spark back. Overall, our relationship has been quite healthy with only a few disputes and we have become each others best friends. I just really don't want to let that go but I don't know how to get our relationship back to how it was at its best, and when he had the most feelings for me.

Thanks so much for any advice its really appreciated 🙂