No sperm, low sperm

Patient: Wife and I are trying to conceive. last year my sperm sample was fine, no issues. last week I went to give a sample and there was no sperm in the sample. again, second sample just this Wednesday, no sperm. I am only taking omeprazole and lisinopril for high bp. but only since august 2013. I do have heart palpitations recently, but only on days it seems I barely drink fluids.. going to have that checked out soon. what could cause sperm to not be produced after a clear sample one year ago?

Symptoms: no sperm