Important question! Please answer.

I have been ttc for 9 and a half months and I've been taking prenatal vitamins for longer than that. My question is could I be accidentally poisoning my self with iron? A woman of my age only needs about 18mg of iron a day but my prenatal has 28 mg and I get iron from food I'm sure. I've been pretty sick feeling lately with strange abdominal pain which is a symptom or iron poisoning. I don't wanna stop taking my prenatals because I'm ttc. What do I do?