sorry, but i sometimes speed-read through the posts, and i missed this:
I told him I cant do this, his behaviour was not normal.
you are absolutely right; this "forgot phone at home" and quick texts to make it look like he's connected to you ISN'T normal. i think that given that statement, it doesn't matter if he is using; you don't want this instability in your life.
and yes, i absolutely believe he's using, after reading the rest of the story