<human>: Give me the gist of the text in a nutshell

My ex (22F) and I (21M) broke up six months ago after a little over three years of dating. The breakup was pretty clean but since then we've had very little contact with just one short text convo and me wishing her happy birthday earlier this month over text. 

I read some relationship advice tonight that made me think back to our relationship and how I could have handled one aspect of it (part of our sex life) much better. I feel a little guilty as a result and would like to apologize to her. I don't know if this would be too weird though seeing as we really haven't been communicating since the breakup.

I should also add that I don't want to get back into a relationship with her, and don't want this to be taken as some sort of hint that I want to be with her again. While writing this I'm starting to wonder if this would send some mixed signals or something especially given the subject.

So what do you all think?
<bot>: I want to apologize to ex about something from our past relationship but don't want to be weird/send mixed signals. Possible or no?