I, too, would be wary of this and second this statement.
Something a spirit friend of mine said comes to mind:
Statements like the above can become a self-fulfilling prophecy, altering your worldview/reality. I don’t struggle with this exact thing, but I have some self-fulfilling prophecies of my own that I deal with.
A suggestion, whether by your ex or an actual spirit (only you can know from your experience the validity of whether or not he was actually possessed), can completely change your trajectory if you allow it. I second the previous suggestion:
I’d also advise not doing any occult work for a bit of time to clear your mind of the prophecy, or building up an “I’m not going to let this dictate my life” mentality. Much easier said than done I realize (because as I mentioned I’m struggling with this myself in other areas), but where I was able to overcome the hurdle I realized that previously held belief only had as much power as I allowed it to.
I say this because of a quote I read from @Lady_Eva that really vibes with me (this is not the exact one, but I couldn’t find the other):
(Just my opinion and experience:) If magic is an act of will, we can will ourselves to break these loops. A great thing to me is that you know the moment it started, so you can break it before the suggestion completely destroys your life.
This is also just my opinion. Hope it makes sense (I feel like I rambled there).
Been there. I hope things look up for you soon, friend. 