How do I cancel my BTC transaction (Unconfirmed for 5 hours)? am using blockchain.info.

You can see the transaction at https://blockchain.info/tx-index/7122f25e4d2e79d5a93cf3797de44b00625cb8407d49c9fce0434f9d3cf32a82?show_adv=true

HERE IS MY OTHER TRANSACTION THAT IS UNCONFIRMED: 
https://l.facebook.com/l.php?u=https%3A%2F%2Fblockchain.info%2Ftx-index%2F8290eebdbd663b27b428979b9d2b55f4171d62fbb6e81e09100f6f7788e02a14&amp;h=8AQHbDyU2

I added a small fee, but my transactions are usually sent alot quicker than this. 
What could be the error? Also, more importantly, how do I cancel the unconfirmed transaction and get back my coins?
There's not really anything you can do, other than wait. If the transaction isn't confirmed within ~72 hours of sending, it should be dropped from the mempool ie. returned to sender.

The reason your transactions isn't getting confirmed as fast as you're used to, is because the network is a little congested at the moment. It can only handle around 6mb per hour, and currently there's a backlog of around 35mb.