Hi Zuriel. I have found over the counter Ranitidine (Zantac), a H2 blocker (antihistimine for the stomach), has been the most effective for my bloating and reflux. Don't let them talk you into getting a proton pump inhibitor. Your indigestion and hayfever are most probably connected and signs of system wide histamine reaction.
Slippery Elm is supposed to be a natural stomach calmative, but I haven't had much luck with it.
Re, milk thistle. I have used it (not sure of any effect), but it did not aggravate my hayfever.
Oddly enough, peppermint is often regarded as aggravating some GERD issues. From memory, I think this has also been the case for me.
Causes of indigestion could be gluten, sulphites or glutamates, and since you are on a CFS board, you may have intolerances to all three. What causes these intolerances? Wish I knew. I am looking at B12 methylation as a possible circuit breaker.