As bitcoin is becoming successful day by day ,
The number of people using bitcoin is increasing tremendously
This is leading to the sites having a lot of load.
So many transactions together crash the site.
But I can assure you that all the transactions will once be confirmed.
I use bitcoin on a regular bases.
I just pay more fees for transactions to take place quickly.
I do not think that paying more than the fee will speed up unconfirmed transactions. may now occur some problems in blockchain thus causing a delay confirmation. Well, it might be a natural thing, because at this time, bitcoin enthusiasts really multiply.
But the thing is true, if you give more fees or high fess your transactions will take place quickly,in other words, higher fees is there first priority in the blockchain

, that why those who transact with low fees, will be located at unconfirmed transactions which will lead them into traffic. but it will confirm only delayed for a couple of days.