Hi and sorry you have been sick. Anxiety can lower your immune system. Do you eat well? Having a sore throat with a viral infection is normal. I get folliculitis too. It is usually a staph type of bacteria. I don't know where I got mine either but that type of bacteria is common in the environment and on your skin. Maybe you are doing something that causes irritation to that part of the skin?
Regarding the second viral infection did you have a lung infection? Why did they give you antibiotics? Did they do a respiratory culture. Antibiotics don't work on colds. They only work on bacteria. But the doctors over treat with antibiotics and you probably got over it naturally. People can get more than one cold or a cold and flu in the same year and usually it is more than a couple of weeks apart. You usually get a different strain of a virus. It can happen and does.
Do they test your blood once a year for a complete blood count? If that is normal your immunity should be okay.
How do you know you had a Shingles rash? Was it diagnosed by a doctor or did it just look and feel like that?
How often do you shower? Depending on how oily your skin is showering too much can cause you to get dry skin or wear off the fatty acids on your skin that are protective. If you have very dry skin a shower every other day can be okay. If you exercise, though, I would shower after that. Do you clean your towels often?
So far I don't see any problems. I am sorry if you really got shingles so early. You can get a new vaccine that is 90% effective. I believe it can prevent another outbreak. You should check with your doctor on that topic.
Staph is ubiquitous. Basic hygiene prevents it most but not all of the time.
Shingles is not uncommon at your age. Also, it is often an incorrect diagnosis.
I'm pretty sure you've already had a CBC with differential. If not, get it.
IMHO, you also need a full 3 to 4 hour glucose tolerance test to see if perhaps diabetes plays a role.
You should have an exam, with history, etc., by a board certified, competent MD and lab. The MD should also make a decision re testing the competence of your immunological system.