So the posibilities are:
1. Coincidence. I was already ill and by coincidence I got the shot just before the symptoms appeared. (I estimate 50% probability)
2. It was a cold and I was going to get it anyway, but I reduced my chances of getting a nasty strain of flu. (25% probability because it happened so quickly after the shot.)
3. The flu shot enhances my susceptibility to colds? (25% probability?)
It's the last one I'd like to see some research on, because there is a lot of anecdotal evidence that the flu shot "causes flu". Now normally anecdotal evidence means bupkis, but this much suggests that it should be researched. Assume that people have mislabelled colds as flu, the question becomes "Does flu vaccination have a short-term effect on cold virus susceptibility"?
I've googled, and I find plenty of research on flu shot (not) causing flu. And I've also seen plenty of medical professionals stating "of course it can't increase your chance of getting a cold", but I haven't found any actually cited research, which suggests to me that people have just assumed the answer and not actually examined it experimentally. If there is some research that you are aware of, could you provide some links or good google search terms (because I've already tried several)? If I am wrong (which god knows happens a fair bit), I'd like to correct that, but I'd prefer some hard research, not theory and not just "Are you crazy? Of course you're wrong!"