It's a gut microbiome test. I'm from the UK so I wouldn't be able to suggest where to get one from in US but I am sure if you googled it you would find someone doing them. It's a stool test. They send you the results and sometimes do a follow up to tell you how to treat it or you can speak to a nutrionist like I did to go through it with you.

Hi, I have had IBS for 35 years too. I did a microbiome test a couple of years ago as I had a thing about everyone going on about microbiome and probiotics. I had tried several makes of probiotics and prebiotics but they all made me worse. When the test came back I had a chat to the company and their said actually my microbiome was in a pretty good state and were a bit confused how I felt so ill. I then went to a nutrionist with my results and she came to much the same conclusion. Don't know if this will help you!