Baby's Blood Test results

Some of Baby's blood test results back today and they show he is anemic. I should note that he is a healthy, chubby, active, social baby - not sick looking or sullen. So I would have never had known this if I didn't get the tests done.

Results:
iron - normal values are 40-175 and his is 22
ferritin - normal values are 22-322 and his is 5
hemoglobin - normal values about 10.5/11 and his is 9.5
hematocrit - normal values 33-37 and his is 31.7

Pediatrician prescribed ferrous sulfate. I went to pick it up with a lot of reservations because I know how iron supplements can cause constipation. That's the last thing I want is to add another issue for the lil guy. But he is anemic, so off I went. When I bought it, on the bag was written "Place in back of throat so it will not stain teeth." Ack! He's only had his teeth for a couple months and I'm suppose to give him something that might permanently stain them?

Also a few weeks ago we tried the poly-vi-sol with iron. Baby hated it. It taste awful. He vomited it back up. So we stopped that. With this scene in mind, concern about the teeth, and constipation I was hoping for an alternative.

And I got one...
a friend suggested Floradix and I'm glad she did. It's easy to digest and highly absorbable. Plus the taste is so much better. It tastes like prunes (I drank some). More info about this can be found at this link.

I wonder if I return this prescription?

Pediatrician requested his blood be tested for lead since the iron levels are so low.

Now the questions begin...
is he anemic because
1)he has celiac disease or a gluten intolerance and can't absorb nutrients properly?
2) he isn't getting the proper amount of iron in the breastmilk because I may be anemic?
3)there is lead in his system?
4)he has a viral infection? I read somewhere that a viral infection can cause anemia.

I also read somewhere that deficiency in iron or zinc can cause toddlers to bite i.e. themselves, others, shirt, blankets, etc. He's been a biting spree of late. I thought it was just teething, which it still may be.