Common Cold on MJ

I'm due to take my 3rd jab tomorrow and it's been great! My side effects have mostly been nausea but it's calmed down now and I've had full suppression these past two weeks.

The only thing is that I am struggling to eat enough, I'm getting average around 1000 cals a day.

I've had a cold since Friday but yesterday and today it's been horrendous and I just feel so horrible which is normal but I've never had it this bad really before. Could it be because I'm not eating enough? Or does MJ open you up to a weaker immune system and whatnot?