Depending on the symptoms, if its just a cold you should have relief in 3-4 days. Me personally I would not take anything at all based on my history of infertility. During my 2ww I avoided all drugs unless medically necessary like my blood pressure meds, all chemicals, I even switched shampoos and used baby shampoo. We don't know what makes some people vunlerable and others not during the 2ww. Play it safe if you can tough it out. I am sure you will get other advice indicating what you can take. What ever you take your 2ww old baby or babies will take also. So if you can try and tough it out, drink plenty of fluids such as juice and water, use a humidifer in your room if it will help you to breath better at night.
But I have to agree with the previous poster. I wouldn't take anything if it's not necessary. But, actually, I don't really believe cold medicines help anyway. At least they haven't in my experience. But get plenty of rest. Best of luck.
Big no no, only vitamins allowed are those through supplements, unless you are dangerously deficient in one and your RE recommends suppplementing. I had to come off my extra C a day before I started the cycle.