Need help about my medication so if anyone has taken or is taking pregabalin please could you help?

Atm I'm taking 200mg of sertaline for my depression and anxiety, went to the doctors for help with my sleep last week and they gave me pregabalin to help with sleeping and my anxiety.

50mg one to three to be taken at night I took 1 last night (heard many horry story's so was scared to do more then one) but I still couldn't sleep at all... do I just need to take 2 to 3 or do I need to be taking these tablets longer for them to work?

My doctor didnt really tell me much about these tablets so I thought I would ask on here