You need to be sure to take your prenatal vitamins. The doctor will probably prescribe you some with extra iron. If you have a problem going to the bathroom, I believe there are some prenatals that have stool softener in them also.
Your blood volume increases during pregnancy. Anemia (low iron levels) will make you tired and worn out. Take your vitamins, it is nothing to be overly concerned about and shouldn't cause any problems.
I've had an iron deficiency my whole life, but it got worse when I was pregnant. I had to take iron suppliments. They worked well too. I had more energy and wasn't as tire. It also gave me more color to my skin. But it does make it hard to poop.
I have anemia really bad I get my blood checked every three months.
Anyways in a pregnancy you can end up fainting more (passing out)/feeling weak to your legs where you need to grasp on to something or sometimes it just makes you feel kinda of fluish.
Iron does constipate you so you take it with food to digest it easier I take ferrous sulfate(just a pretty word for iron) buy it over the counter and its safe to take depends on mg amount you may have to take two talk to the pharmacist bout it.
Another thing increase you intake with greens(brocoli) greens usually have alot fibre/iron and usually wont constipate you if you take them together!!