I am taking .75 ativan for the last week while my lexapro (escitalopram) starts to work. will i have to taper if i have to take it for several more weeks?

Don't know how: long you were on it. If on it very briefly you may be able to just stop it. If you were on it for longer period of time - than taper is reasonable.

A short taper: It may not cause a lot of physical dependency, but unless there is a compelling reason to stop the Ativan (lorazepam) quickly (high risk for dependency, seizure disorder,past dependency, adverse reactions), a taper over a week or so might ease the transition. Hard to tell how much the antidepressant is working, so it is good to back off on the benzodiazepine a little gradually, esp if anxiety was severe.