Vitamins to take

A

So the past few months my immune system has been shit to put it nicely πŸ˜‚. Has been one thing after another with illness bugs.. colds.. misscarrigeand then colds again. I was on slimming world diet to lose some podge and ended up losing 2 stone and since iv lost weight is when iv caught more bugs etc also in my workplace we deal with customers all the time.. coughing all over you and some not the cleanest of people. What vitamins could i take to help my immune system? That wont effect with trying to concieve? 😊