large stomach, no pain or diahorrea, fuzzy brain

my 8 year old girl has had a large stomach for several years now.  She is becoming more aware of this and is embarrased by it.  She has no pain, no bloating/swelling, no diahorrea, normal stools.  She also is a slow learner and gets confused easily - fuzzy brain??  She has trouble falling to sleep and getting up in the morning.  Her natural sleeping pattern is 11pm and waking at 10am.
I have removed gluten from her diet but after one month have seen no difference in stomach or confusion.  She began to get pain a few times after drinking milk but no problems with cheese, ice cream chocolate.  I have switched to A2 milk which does not seem to give her pain.  We do not drink/eat a lot of dairy anyway - one serve maybe every other day.  Since removing gluten she does not eat as much.  Maybe coinsidence??  She does not like fruit - only eats apples and once in a while a banana.  She does not like fruit juice only apple.  Vegies are limited to potato, corn, peas, beans, broccoli.  She tries other fruit and veg every now and then but spits them in the bin.  She likes a lot of protein sources except egg.  Sugary and processed foods are limited in our house.  
I am concerned about her slow progress at school.  She tries so hard all the time struggling with every subject.  I cant help but think the large stomach might be a key that something in her system is not right.  
Does anyone have any ideas what I can do to work out if there is a problem or if it is just how she is.