It's easy to overly worry about these things but there are plenty of viruses going around all the time. I caught a bad cold from my nephew in September and it didn't clear up properly until December. Then I realised I was sleeping with my mouth open and that just made things even worse. I thought the sore throat, cough and nasal drip would never go away and then it suddenly did. I had a blood test and weirdly, nothing came up.
By the way, I have always reacted badly to synthetic progesterone and when I was on the pill years ago, I had continous sore throats and nasal drip which caused tonsil stones in the end, it went on for years. I also had this when I took continous combined oral HRT and I sometimes get it very slightly now with with cyclical Utrogestan. Something else to bear in mind.