Opinions please!?!?

I feel like my SO does not understand me mentally. I have tried multiple times to explain my mental health to him but sadly he just does not understand. While I don't expect him to know what to do a little effort would be nice.

A few days ago the guy I was trying to get over when I met my current SO texted me saying he still has feeling for me. As much as I wish things could have worked out they didnt and I'm happy with my bf now. But it did make me think about how much I miss having someone who gets me and it's not always so hard to make it work.

How can I make things better with my SO. I really love him and want it to work out but I'm not getting what I need and idk how to make him understand.