Are my anti-depressants working?

I have been taking Cymbalta for a month now. I was feeling depressed, especially on the weekends, and after a trip back home (I'm currently in college) and an amazing time with friends I felt really good, but then my prescription ran out. I don't know if the pills were helping or not. I'm on 30 mg, and I think it may be too low a dose for me. How can I tell if they're working. I felt the same even after the time the doctor said I should feel different. I don't know if they were working or not. Can anyone help me? Generally I take higher doses of medication because my body isnt that susceptible.