I Lived In Africa Over A Period Of 20 Years.

I lived in Africa over a period of 20 years. I was treated for parasite infections on different occasions, including infection with Entamoeba Histolytica. Since returning to the U.S. 5 years ago, I have suffered on and off with what I thought to be IBS. If I want to be sure it's not perhaps extra intestinal amebiasis, what steps should I take? (An earlier stool test was negative.)