It is not wrong to see a sex worker, and you are not a bad person for seeking the help of a sex worker.
Using condoms every time is a great way to protect yourself from STIs! It isn't guaranteed, however -- there is still some chance that you can transmit STIs when using condoms. That's why we recommend pairing condom use with getting STI tested regularly. If you can, I would recommend getting tested a few weeks after sex with every new partner, and waiting to get your results back before having sex with a person other than them. If, at some point, you have only one sexual partner, you should still get tested every 6-12 months as a preventative measure.
Here's our article on STI testing as a refresher! Testing, Testing...