Is it normal for anxiety to randomly come back?

Anxiety and depression tend to come back, though it's somewhat dependent on what's going on in your life. Everyday things and major life events always cause some amount of anxiety, but it's a manageable and healthy level. It's when things starts adding up or something major happens that causes a major amount of anxiety that it becomes a problem again.

If you have gone though it before, it should be easier to deal with the next time around. It's kind of like having the flu, then getting it again. Your body will be able to fight it better because it's better equipped this time, but instead of it being your immune system that will fight it, it is your knowledge base and experience.

Want to have sex?

That sounds like a normal cycle for anxiety. The fear of the fear is often the hardest part to overcome.

To an extent, I think you just have to work through it and let it run its course and remind yourself that most of the symptoms you feel is just anxiety.

I'm not a doctor, but I think it would take many years of chronic stress to cause any significant damage to your kidneys.

Just know that you're not alone, and that what you feel is "normal" and that it is experienced by many people. Everyone kind of finds their own way to work through it.

Hypocondriacustotalicus!!!