Michsm, I'm sorry you are so down. I hope you start posting more, you have a lot of experience to share.
Not being in your own place could be part of it, for sure. In the six months since the divorce, what have you done for yourself (as in self-care)? You were together for 10 years, so it's been some time since you were single, that will take some getting used to.
Do you have a social circle at all, or even a couple of close friends you meet with sometimes? Family? What do you do for fun, if anything?
Oh and next time he texts, I hope you will ignore him. It would be one thing if he had texted to let you know that someone you both know had a car accident and is in hospital, that's considerate, to just be sitting there doing taxes and decide to involve you because it's a shortcut is inconsiderate considering the circumstances, you are not on "friendly" terms with him (which is perhaps why it's triggering).