i read this the other day when you posted, really thought i replied, been a lot going on in my head that i been blocking out, and actually forgetting few things, so apologies for delay in welcoming you.
don't really want to repeat anything that's now already said, but just wanted to add, that i think its so great that you've said when you get through this you want to help others.
My friend is a brilliant artist, and went through depression without meds and did therapy. few years since then she now does art therapy in community.
so you use your art as a therapeutic way to calm yourself or express yourself, might help, while waiting for professional support.
I think creatives (well its said that we often suffer from over active brains, and can trigger depression or mental health easily, particularly overthinking) but i do think your ex behaviour (his negative self talk to you & drug use, is also a factor). But as with everything, with right support (all round support) you can get through it.