Hello someofusrbrave and welcome.
Having an eating disorder which can be traced back to childhood is something I can definitely relate with.
Have you considered seeing a gastroenterologist,with respect to your digestive problems? With all that the body goes through during binge and purge cycles enough,gastrointestinal problems are to be expected.
Another thing to be considered is seeing you family physician,with respect to having a complete physical performed(including blood work for electrolytes,etc.).He/she may prescribe you a prescription antacid and/or suggest you see a specialist,with respect to your digestive system.
With respect to your therapist;now's the time to be proactive.The session is about you and your concerns and her professional opinions based upon the information provided.
If you have to stay with her,work it to your advantage.
Write down questions you have during the week and take them with you.
Show her that you can be organized and mean business.
Getting better should be priority number 1 and that sometimes means going back in time to resolve conflicted moments.
You can do this....believe and you will acieve.
If you truly want something you've never had before,you need to be ready to do things you've never done before.
I'm rooting for you.