Immune System Out of Wack?

# Female. 45 years old. Only meds are estradiol for HRT since I have a complete hysterectomy and oophorectomy due to severe endometriosis ten years ago. Recent mild proctitis diagnosis. Non-drinker. Non-smoker. Probably since my 20s, everytime a flu or cold is going around, I seem to not catch it in the way it's presented in others. I will feel like I'm coming down with something, pretty quickly develop a rather high fever, and ... that's it. Sometimes these fevers last for days, but the illness never develops. No stuffy nose, no sore throat, no cough. In fact, I don't remember the last time I had a legit, "traditional" cold/flu. The fever makes me terribly nauseous, but that's about it. However, it's still debilitating, moreso than any cold/flu. I often have to miss work because of it. Then when I get back, everyone probably thinks I'm faking it because I don't have any lingering cold/flu symptoms. It really sucks and I wish I knew why my body reacts to illnesses like this. I do have an autoimmune disorder (ulcerative colitis), but I'd expect my body to get every cold/flu symptoms in the book - not this. Do I ever really even "catch" the flu, or is it just a major overreaction of my immune system, destroying the first sign of the common cold/flu? What is this?