Advice needed: How to not ruin friendships?

Hi!

This is gonna be a long one, I'm sorry.

I have been diagnosed with Bipolar and Anxiety, and ADHD. I am in the process of getting a Borderline Personality Disorder (BPD) diagnosis this month. Regarding all these diagnoses, I have run into many issues that stem from my symptoms that I can't seem to get under control. I am very emotional and not really good at communication, I seem to take things too far too fast, and my emotions and moods change rapidly daily. Because of this, I have had multiple emotional crashouts.

Recently, I went through a friendship break-up. The friendship developed over six months and ended on a bad note. It was mostly because of me, but at this point, I'm not blaming myself anymore, nor my ex-friend at all. I've come to realize that there is no point in blaming myself, since that doesn't change anything anymore.

The friendship ended because during those six months, I got very attached and obsessed with my friend, and I also developed romantic feelings for her, which probably also was part of the reason why things blew up. We talked daily and hung out many times during those six months. I also have a very deep fear of abandonment, and I got very anxious whenever she left me on seen and didn't reply to my messages right away or for many hours.

This brought up many arguments between us, because I was anxious and insecure for being left on seen. I explained myself and apologized many times, and most of the times we made up and went on with our communication. The last argument stemmed very strongly from my anxiousness and insecurities, and also stepping over her boundaries, which I of course regret. I had no bad intentions with these aspects, and I tried explaining it to her, but in the end it was too much for her, thus she decided that that's it. She unfollowed and removed my follow everywhere.

Since the end of our communication, I have had bad anxiety that I even resorted to taking diazepam many times. One reason is that we are in a friend group that has a group-chat and we are both in it, but we pretty much don't really acknowledge each other on there. Other friends in that group are aware of the situation, and I have asked advice from some of them, as well. I still sometimes feel anxious and uncomfortable texting in that group-chat because of what we went through.

I started therapy again, where I have made this situation the main focus right now. My fear of abandonment, anxiousness, and insecurities regarding friendships.

So, I guess I would like some help on how to navigate my fears, anxiety, and insecurities, and what kind of steps or actions I can take myself individually to manage myself better and not ruin anymore relationships.

Thank you in advance!