My iphone 4s will not locate or connect to any wifi network

Since yesterday, all the sudden my iphone 4s disconnected from my wifi. After that, it just basically stopped working- it can not locate any wifi network anymore and even if it does ( located wifi only twice) it can not connect to that network. On top of that, its been freezing a lot. I tried turning it off/ on, resetting the network, but nothinng worked. Help?