I've just created a thread on iron-deficiency (waiting for response too) before I saw yours so I'll just tell you my experience of the last couple of months.
Basically, take the iron tablets, Pregnacare and Spatone are not at all sufficient and won't make a dent in it. Iron CAN make you constipated but it's not automatic. Make sure that you take the tablets with orange or prune juice as it helps to absorb (and prune juice helps with possible constipation, although it tastes foul imo) and that you eat plenty of fibre, baked beans, wholemeal rice and bread, red meat, spinach
I was extremely low on iron with my DS and taking the tablets took me from about 7.0 to normal range (around 13 I think but I can't be sure, was nearly 2 years ago). I had to go back and get ferrous fumarate prescribed instead of ferrous sulphate. Badgerwife is right, spatone won't touch it. But try and get plenty of dietary iron too. I ate spinach and dried apricots like no one's business.
You def should take them - your body creates a third more blood during pregnancy. You must take with vitamin C - Oj - to aid absorption. this also helps combat nausea. You can use things like flax seeds to stop being a bit 'bunged up'. The baby takes what they need first - you get what is left over. It can make your vomit more (i found this) if you are very low in it. I can't eat any meat due to preg. aversion and extreme MS throughout pg so far (although this is now once a week for a night..!) so I found taking first thing, with OJ worked best.
The tablets will work but do make me constipated. Lots of friut juice helps. The tablets did not work for me but I seem to have an absorption problem. I ended up getting a iron transfusion. I have another 2 to get!
Before I got pregnant I had problems with seriously low iron (hair was falling out and was having chest pain every day) I took Ferrograd C for three months and made a huge difference. I've never taken it whilst pregnant so don't know if it's suitable - but maybe worth asking the doc?