Hi Jess,
Many people take more than one medication but you always have to way up the benefits vs side effects/risks.
Officially the combination is listed as "moderate interaction risk".
Most doctors won't recognize signs of interaction so it's good that you are taking some control of your treatment. The doctor titrated the Elavil slowly, that is normal practice when combining.
Was the Lexapro causing insomnia or other problems that requiring the addition of Elavil?
It's always safer if you only take one type of antidepressant or chemical that acts on the central nervous system. Your right, by using the same pharmacy for your medications, they should check not just presciption meds but also "over the counter" meds like cough/cold remedies, they to can interact.
Nick