Possible UTI or Prostatitis?

Patient: I am wondering if someone can help me to narrow down some of the symptoms I have had. For the past week or so I have had a mild to moderate stinging after I urinate. The pain is normally at the tip of the penis to a couple inches inside, and while it never occurs while I urinate, it is still rather uncomfortable. It is also slightly red around the tip, which I assumed was from irritation or an allergy. It seems worse with tight fitting clothes, and comes and goes in severity throughout the day. I had a UTI test done yesterday at a clinic but it came back negative. This also happened once this summer, but this time it is lasting a lot longer. It cannot be from an STI, since I haven’t had sexual contact for a number of years. I do have some low back pain, although it could also be from straining myself the past few days while at work. Could this be something like urethritis or prostatitis?

Symptoms: Burning, discomfort, low back pain