Can my toddler have Celiac Disease?? please help!?

My son is 18 months and is underweight. His weight gain slowed down around 9 months and I have been EBF since birth and still am BF. Not exclusively of course. But he only passes bowels every other day, sometimes everyday though, but onle once. He also seems to struggle everytime he goes like it's hurting him =( but sometimed, his bowels aren't even hard. He is an ok eater, I think he just takes after me in this area. I am 22 yrs old, 5'2 and weigh 100 lbs. But a few weeks ago he was throwing up for a few days and we thought it was a virus, it passed. But now he threw up twice today, but it may have been motion sickness and drinking too much water?? Idk, I just want to know what people with toddlers who have celiac think...he also has A LOT of hair, 12 teeth and is walking and running and a very happy child. Very smart as well. His iron level is low according to the WIC clinic, it's a 10.8. Any help would be greatly appreciated. Thank you and God Bless!