What do you wish you did differently?

I wish I told the main friend who didn't like me anymore due to me stressing my friends out due to my health problem when she asked me is the health problem due to weight (I am underweight) that it's about something at the time and the fact that the other person in the friendship group doesn't know about what happened and the health issue before I dropped out because another person who I was on good terms with without complaining to her wouldn't have blocked me. I also did tell the main person after I left on messages what the issue is and she blocked me and informed the person who added me online who I was on good terms with to block me as I was complaining and other extreme things I was saying and doing and it looks like I did it for attention to them when I was suffering. So let's say I had M online and didn't complain before I left A Levels after one year and was on good terms with me as I was not complaining and she used to come back for me if I forgot where my exam was showing she cares and validates me and my issues, I was complaining to the other 2 genuine friends F and Z and 1 evil one N who invalidates me and issues and wants me to fail and I wish I had told F what the issue is when she asked and N doesn't know what happened and what the issue is.

At the same time I basically messaged F after I left about what the issue is and they got the one I didn't complain to, M to block me as she found out what happened before I dropped out of college.