I need help

Me and my ex dated for over three years, we were both eachothers first. She broke up with me because I had my own issues to work on. I been working out, going to therapy and actually am feeling a lot better now. During this time we were going no contact. In a way we both broke this and she stated that she misses me in her life because I am her best friend. I agreed we could try being friends. Every time I asked to try to do something the plans always fall through. We have plans to workout (we go to the same gym and used to workout together) next week. Im not sure if she is going to make an excuse to not be able to do it.

My problem is im at the point that I just want to message her and just break everything off and tell her I cant be friends and that we should just stop talking all together. Its just to upsetting having her do this