You can take vitamin C and vitamin D without a problem. However, I would not recommend you take echinacea while breastfeeding as we do not have enough data on its safety for the breastfed baby (nor enough data on its effectiveness on the common cold if you ask me 😀).
You can also use Tylenolâ„¢, Advilâ„¢ or a spoonful of honey if you have a headache or throat.