Prenatal vitamins

Hi, I'm 15 weeks and 3 days. For like a week, I did not have my prenatals because they were gone from literally every store I checked but now I've finally got them. Its been 2 days since I've been taking them again and I've had horrible headaches and today, I almost fainted, just haven't really been wanting food, and continued headaches. I've just been feeling miserable. I'm wondering if I'm feeling like this for taking my vitamins again after the time missed or could this just be a coincidence timing and be just a crappy few days?