Each wallet behaves differently depending on how the creators of the wallet decided they wanted it to work.

Therefore, suggestions such as "wait until some miners includes the transactions in a block" or "cancel those transactions by running bitcoin qt with -zapwallettxes command" might be useless and invalid advice.

The first thing you'll need to share with us to receive good advice is what wallet software (and what version of that software) you are using.

In your post you state that you used Bitcoin-QT in January, but I assume you either used a different wallet this time, or you changed some settings on your Bitcoin-Qt wallet because Bitcoin-Qt doesn't re-use the same bitcoin address when you have the default settings.

If you used an old version of Bitcoin-Qt with modified settings, then you probably should upgrade to the latest version (now called Bitcoin Core).  As longbob72 has implied, recent versions of Bitcoin Core include a command line option "-zapwallettxes" that will remove unconfirmed transactions from your wallet.

If you have upgraded to a recent enough version of Bitcoin Core, then after using the -zapwallettxes option, you can wait a day or two and the network will forget about your two unconfirmed transactions.  Once that has happened, you can create and broadcast a new transaction with your wallet.