I have had some success, but not complete resolution of symptoms. However, I have functional dyspepsia, not IBS (what the low FODMAP diet is indicated for). The thing to remember though is that it's meant as a temporary, meaning for a few days and usually no longer than 2 weeks elimination diet to see if symptoms improve, and then you can slowly add back in various categories or foods to see what you can tolerate and by how much. The reason they always recommend to do it with a dietician is because sometimes people feel so good on the full elimination that they don't progress the diet, and that can cause long-term issues.

In my case, limiting foods to strictly resulted in food stress and disordered thoughts about eating (which had literally never happened to me before) which is a known risk for people with GI conditions (understandably). I never thought it would happen to me, until it did. I'm now working with a GI-trained dietician who was able to help me be more strategic and liberalize my diet.

Sorry about your troubles; it is not comfortable and very stressful.

Do you have plans to see a gastroenterologist or your PCP if the wait is too long? They may want to rule out other potential causes first.