Hi and welcome. Well, first, protected sex eliminated your risk of std's. That is not a concern here. You've had a lot of off and onS again issues with bacteria. First, let's make sure you are wiping the right way (not to be too personal or gross). You should always wipe after using the restroom front to back. Okay, whew, got that out of the way. Now, I would do one last urine test and do not take antibiotics until the results come back. They should have them within 24 hours when they test your urine for bacterial. If it is positive, go for another round of antibiotics but also incorporate probiotics into your routine. The supplement type you take in a pill or the yogurt you eat or drink in smoothing form. This can greatly impact your ph balance.
Has your urologist checked you for kidney stones? Bladder stones? Those can cause this situation. Also, an abnormality in your anatomy. That can be checked. The issue with improper wiping in the bathroom or sexual contact that would transmit fecal matter to your urethra is another one, And lastly, I don't know how old you are but some pre menopausal women get this due to hormonal shifts. Some women will take antibiotics for an extended course of therapy-- even up to six months. Which seems long but it is done from time to time when necessary.
Let me know what you think!