I am not in the medical profession but I do a lot of research/writing regarding various health issues.
The immune system has the job of protecting us against invaders - germs, virus, bacteria etc.
The immune system is similiar to a small army. That turn up to defeat the unwelcome visitors.
The bowel has bacteria both good and bad - if the level of good and bad is not close to accurate about that means that the little soldiers in the immune system have to participate in helping clean the bowel instead of doing their correct job of cleaning out the invader dangers only.
If your bowel is causing you any sort of problem that may be your link. A good probiotic will help correct that. (If you need help with that - there are a few things to know before purchasing any so contact me and I will fill you in that)
Other than that if you are getting enough sleep, eating a healthy diet and get enough exercise and fresh air - I would probably visit my doctor and ask for a blood test - just to see what is going on and whether the problem may be a little more involved.
Keep a big pack of tissues on you and wash hands regularly. Don't rub your eyes often either that is a lovely entrance way to little virus bugs.