From the answer given here, the unconfirmed transaction end point seems like what you want. As explained there,
The returned object is an array of transactions that haven’t been
included in blocks, arranged in reverse chronological order (latest is
first, then older transactions follow).
unconfirmed means the pending ones.
Or you can connect to the live network itself via web3 and use
eth.pendingTrnsactions either by running a full node or using a service like metamask.
As @Prashant suggested in comments,
eth.pendingTransactions may be returning pending transaction in mempool of the node you are connected to. And In case your mempool is full, you may miss a tx that is pending =. It may be in pool of others node.