As far as I remember, transactions are usually stuck in the mempool for 2 weeks or so. Unfortunately, transactions made on Bitcoin Core 0.14.0 can't be Replaced-By-Fee by default. You could try abandoning the transaction but it's a bit difficult and might be a bit risky. This article on Bitcoin wiki describes the whole process in an understandable way. It would have been much easier for you if you had upgraded your software.