Stomach/Colon Issues

A little over a year ago I started having some stomach/colon problems.  I had tons of gurgling in my stomach and colon area and a general feeling of having trapped gas/air/bloating all over.  My bowel movements started changing.  One day they would be fine, the next day they would be kind of skinny, then one day they would be weird puzzle shapes, the diarrhea, then back to normal, and on and on.  

I saw my doctor.  He pushed around on me and said he didn't feel any lumps.  He pushed quite hard in two different spots, saying he was checking my gallbladder and my appendix -- I felt nothing and he said all was fine.  He ordered a blood test to check my liver function and "check out my gall bladder to some degree" -- tests came back normal.  He was considering doing some true gall bladder tests but said he suspected maybe an ulcer, gastroenteritis?, or maybe IBS.  So he prescribed me Hyoscyamine and Protonix, saying he thought maybe the odd shaped poops were being caused by my colon spasming and pushing them into odd shapes.  Within a day everything returned to normal, I felt great and my poops were back to their normal shape and size.  On follow-up the doctor just told me to keep taking the medicine and prescribed several refills.

Over time I have noticed that things are mostly fine, but occasionally I will have the strange shaped poops again, but it occurs much less frequently.  

My question is that I have been reading some things recently that make me think maybe I am treating the symptoms but not whatever the actual cause of this is.  I am just wondering if I should be concerned that something else is going on here and go back for another visit and ask for more tests or if that would be overkill at this point?  Does my treatment sound reasonable, etc.

Thanks for any advice you can offer.