Why do I get sick every single weekend?

For years I have been getting sick in the form of nasal congestion and a runny nose at the same time, along with violent sneezing attacks, pretty frequently. At this point it has become a weekend routine. The doctor tells me to see a psychiatrist. The psychiatrist tells me to see an allergist. The allergist says to see a doctor. I am taking vyvanse to help me concentrate in school and at work and seroquel to help me go to sleep at night. During the week, I have school and work every day for most of the day. During the weekend I have my son and his mother over, and as much as I love my son, he stresses me out. What the hell is wrong with me, and what can I do to fix it? This is ruining my relationship with my son and it has gotten to the point where I can't get ANYTHING done because I'm busy all week and can't leave my house on the weekends.