Post workout illness.

For the last 3 weeks I've started back at the gym two to three days per week. I've been taking it relatively easy and everything has been ok until this week. On Monday I trained my upper body, pushed myself to almost failure on the bench and to failure on the shoulder press. I put in some seated rows and dumbbell raises, nothing crazy. I had what for me, is an amazing sleep, 7-8 hours and only waking up once or twice, but when I did wake up I felt very stuffy, like I was coming down with a cold, inflamed even, and that has carried over to today, blocked nose, malaise, sneezing, again, like a mild cold. I have noticed this happens all the time after a spell at the gym, AI has suggested a few possible problems. Either I'm catching bugs at the gym or I'm suffering from some sort of immune system issue, but, I've had plenty of blood tests these last few years, although admittedly not for around a year or so. I'm leaning towards a reaction to my workout and not a virus as I don't have all the virus type symptoms, just a feeling of systematic exhaustion. If it is this who am I better off going to see, a doubt I will get far with a GP? Have any of you experienced this and do you have any suggestions on how to aide recovery and prevent this in future? I've read it's best to eat plenty of carbs post workout as carb depletion can cause these symptoms, it's not something I've really done, I have only really consumed protein after a gym session. Any tips will be appreciated. just to clarify, I'm a 41 year old male, 185cm & approx 112-115kg, non-smoker on no meds with no diagnosed health conditions although I do suffer from stress & anxiety.