U will want to see a GI Dr....this Dr specializes in the digestive tract...and as Flycaster mentioned u do need to take the meds at least 30 to 60 mins b4 u eat,,,,and do not take other meds or vitamins along with it as they also can affect this med.
U will also need to avoid foods that are adding acid to ur system.....this will help u make sure u r doing all u can.
The GI Dr can do testing (not blood test) to see if u have high or low levels of acids as they both will have similar symptoms but are treated differently.
Chewing gum can also help as eating several small meals a day...the saliva created when chewing/eating helps break down the acids....
And the foods also use up the xcess acids to be broken down....so less laying in ur stomach.
IBS can be related to how u feel with this,..so do not think it is not....
Do get to a GI specialist and have testing done.
See the health pages for foods to avoid and lifestyle tips to use in the meantime, -
http://www.medhelp.org/health_pages/list?cid=236