Not really and that is a good thing!
A stronger immune system would destroy your own body (like those of some people).
A immune system must maintain "middle" strength at all times! Too low and you get sick very easily, too high and it would kill you itself.

My immune system is so powerful that it ruined my digestive system, so I have to take immune suppressant to prevent it from getting worse.

Stress is a pretty big factor in your immune health. Take some time to relax. If you’re not getting enough sleep, that’s also gonna affect it.

Hmm... I would say the obvious: Eat healthier and exercise :P
Bettering your physical condition can power up the immune system in a natural way.
Also if you're dealing with anxiety and such (like most of us do), it will also help your mental state, which will also affect your body.

Relax, take good meals, nutritious meals, do some yoga. Whatever helps you keep going.

Honestly,
Stress really messes with your immune system,
Lack of sleep hurts its quite bad too,
Mine is pretty good most of the time, but the moment i sleep less then 4 hours in 2 days , i will get sick asap.

I eat a lot of mandarins and oranges, i love drinking fresh orange or lemon juice with some honey and ginger, usually makes me feel a lot better and it sooths my throat.
I also heard from my grandma that eating oatmeal with bananas will give you energy that burns slower, might make you less tired.
But well mentally, try doing things that relax you, enjoy your favorite music, eat things you enjoy,
Get some fresh air and get on the sun a little bit, even if you are just looking through your open window.
Maybe get cozy and watch a show or some movies you like. ^^

Lack of vitamin D from sunlight certainly will lower the immune system. Winter being the worst time for this to occur. Eat healthier, nutritious food and regular sleep.

I work very poor hours some weeks but I work out in the sunlight most of the time so I attribute that to myself rarely getting sick, even if family or coworkers are ill.

Vitamin C, D3, and Zinc. I like to drink a lemon/honey tea with a splash of apple cider vinegar, too.

Vitamin D, Vitamin C, and Zinc, plus a Daily Vitamin with tons of other stuff wouldn't hurt.

Also: lots of water!

None of this will make you Superman but you'll feel a bit better and fight generic viruses off easier.

Vitamin D, Zinc, and QBC really helps strengthen it. Also I’d say research herbal vitamins!

I always recommend gummy/chewable vitamins because they're a lot more enjoyable to take every day. Sorry you're unwell and I hope you'll recover soon!

Well ironically the more contact with the outside world the better off you are, because your body gets immune to certain bacteria and fungi, and of you live in your own bubble and never go out. If something aka someone brings in a foreign contaminate into your bubble, you have no way of fighting it off.

Exactly. The longer you stay inside a bubble, the weaker your immune system gets. Have to try and go outside, and get your body the right vitamins, but also try to not rely overly much on multivitamin and supplements. Better to get vitamin D from the sun rather than just a supplement, a supplement is fine if you have no alternative though. Also exercising and all that.