Are you able to get a consultation via your insurance or otherwise, with a clinical pharmacologist? That is a pharmacist with a doctoral degree, and they are usually trained to spot interactions between groups of medications. Some have a thorough knowledge of psych meds. You could ask at your pharmacy. I'm also assuming you know that the rebound from a stimulant will be fatigue (I take a very low dose of Adderal and notice increased fatigue about 48 hrs after the last dose, but I'm a lightweight). The Ativan, depending on when you tend to take it, could amplify this effect as well.