Always when in doubt, check online block explorers (at least two as all of them are buggy to some extend and might freeze for some hours/days):
blockchain.info
insight.bitpay.com
blocktrail.com/BTC
etc.
...is your transaction there (you can search for your receiving address)? Is it confirmed? When it is not there at all you know it is not problem with your local wallet. If the tx is there you have probably problem with synchronization of your wallet - you can try to select different server to connect to (in Electrum's settings). You can also try running Electrum with different directory ('-D' command line parameter) to force it to download its metadata again and recreate your wallet from seed. You can also try to install Electrum on different machine & restore your wallet there. Maybe check your firewall, too.