If your transaction is not being confirmed, and you did not use replace-by-fee (you almost certainly did not, very few bitcoin wallets support this) then you will have to wait for the network nodes to drop your transaction from their mempool before you can attempt to resend your transaction.
After 72 hours of being unconfirmed, most mempools will drop it (nodes with default settings). If volume is particularly high and mempools are completely filled up (beyond 300MB for default settings) then it will be dropped sooner. However there is no way to know if your transaction is being dropped or not, beyond just going to common blockchain explorers and seeing if they have it. Blockchain.info has very liberal node configurations, they keep almost every transaction. Chain.so is an example of one with conservative settings, they are likely to drop your transaction before other explorers and nodes.