I am sick, and have been eating a bunch of junk food, any ways to improve my immune system?

I got sick Thursday, and have been coughing ever since, I missed school Thursday, but went Friday. I have been just laying around the house all today, eating junk food, and I’m worried that maybe my immune system is WAY down, I need my immune system getting better by Monday, any ways. This is just allergies, but I am still afraid. I’m a germaphobic btw!

Also do you think that I may catch something??