frequent vomiting

[herdaughter]

My son is 12 and has frequent vomiting episodes ever since he was very little. I would say he vomits approx twice a week, almost always in the morning, sometimes in his sleep because he will wake up in the night from vomiting, then wake me up. My doctor has always said he was fine that it is normal. It seems to slow down for a bit then come back every couple months. I'm not sure really, I just know it is often. A few months ago I have had my doctor do some tests as he tried to convince me that he is fine (it doesn't seem fine to me) and ultrasound and blood tests came back ok. His school is concerned, because he misses a fair bit because of this... or he gets sent home from vomiting all over his desk... floor... it just hits him. My doctor said it is stress, but he said he isn't stressed.
This morning when cleaning his vomit off the carpet i noticed that there were pinapple chunks in it.... and he had pizza with pinapple on it 36 hours before that.... at least... it was like 2 days ago. I've noticed things like this before... doesn't it take 6-8 hours to digest food?
He says when the feeling hits him it comes so fast, he feels sweaty and dizzy and his stomach hurts, then it comes out so fast that he usually cannot make it out of the room, sometimes even his seat.
He is also underweight, as is his father... and takes 1 or 2 bowel movements a week... sorry if that is too much info
Does anyone know what might be causing this? What tests I should be asking to be done?
The only stomach condition that is in my family is crohns disease. Any info???

[mammo]

I would get your son in to see a pediatric gastroenterologist regarding this.  I agree with you, something is wrong, and if it should (which I highly doubt) turn out to be stress, then this too needs to be addressed.  This is going to start affecting your son in an adverse emotional way, and it's so unfair to him.  There are several things that could be causing this, motility dosorder is one.  Get him into a specialist and don't stop until you have your answer.

[herdaughter]

I forgot to add that after he vomits he is tired, usually naps for an hour then wakes up fine