I have experienced this same problem with my son. He did out grow it. Just to give you another idea of what it could be I thought I'd share my story. My son suffered these attacks when he was younger and always at night. I did end up taking him to the ER a couple of times and sometimes it was actually the beginning of a cold. It just seemed to be an indication that he was getting one. However, it was very scarey at times. Also when you said he felt like he had to throw up, my son also suffered from this type of thing too, we found it to be that if he didn't eat right or ate too late the night before, then he'd get sick. Acid reflux. But like I said he did out grow it, we just made sure he didn't eat too late and what he did eat wasn't anything too rich or spicey for him. Another thing that I'm familiar with is anxiety in my daughter. She started as young as age 3 if not before. It may be a nightmare that started this for your son but if there is anxiety, I think you will see other signs. My daughter went through a lot of different stages, but night time was more about not wanting to be alone and with your son saying it was ok for you to go back to your room makes me think that it wasn't anxiety. But I'm not a doctor, just thought I'd let you know what I've seen with my kids and maybe it would help. Let me know if you have any questions for me!