I occasionally take both. I take the Ativan for muscle spasms. However, I only take 1 0.5 mg tablet. That 1 tablet lasts me a good 24 hours. It may be that taking 0.5 mg at night and 0.5 mg in the morning is too much for you and that is what is making you so sleepy. (I know it would me but I'm a light weight.

And, it only takes about an hour for the Ativan to kick in and start working for me.).
Next time, maybe try skipping one of the doses (either morning or night) and see if that makes a difference.
And, B2Y does have a good point, always check with a dr. before changing dosages on regular medications and/or talk to the pharmacist about it (many times they are more knowledgeable than the drs. on medications, interactions, side effects, etc.).