Those symptoms are consistent with hypothyroidism, however, there could also be something else going on that a doctor would need to look at. If you haven’t had your thyroid levels checked in a while, I would suggest making a call to the doctor about your concerns and tell them about the diet as well.
As a pharmacist, I think you should definitely get the flu shot. Even if your body is a little stressed it shouldn’t affect your body’s response to create antibodies or make you feel any more run down than how you usually react to a shot. Remember it takes 2 weeks to build protection and you’re more likely to pick up something more easily in that 2 weeks. So make sure your hand hygiene is good and you’re washing all your veggies well.