While too much iron can cause problems (I usually suffer from high iron as I have a condition called Haemochromatosis - literally translates to abnormal condition with iron in the blood), I think you would need to be on a very high dose for a significant period before you would get to that stage, especially while pregnant. In people who don't have my condition, the excess iron is excreted and not absorbed anyway. But I agree that you should get medical advice.

Interestingly I actually had lowish iron for the first time in my life in the late stages of my first pregnancy and suspect the same will happen again this time. I only took one supplement a week though. It was funny doing all the things I normally avoid - like eating iron rich foods and vitamin C.

Good luck!