Yep it should be fine ive done DXM and Clonazepam before and been okay and i don't know of any dangerous interactions between DXM and Lorazepam, at least in reasonable dosages.
Did you take them at the same time? If not, what order?
I am thinking about dosing the Ativan first, so that if the subjective effects are unpleasant it will wear off before the DXM. If I like it, I can redose.