Which version of PS and OS?
I assume you draw out a type area with the Type tool before pasting in (or typing in) the text.
It might be worth resetting your Photoshop preferences.
Are you by any chance using the centre text tool in the options bar.:
If so then the text will jump to the left as it will centre around your original cursor placement (which presumably was at the left of your typing).
If you want to centre the text on the page choose the move tool , click on your text layer - then select all (Ctrl+A /Cmd +A) then use the align layers icon in the Move tool
If that is what you are doing - please post a screenshot - before and after alignment - including the layers panel and options bar