Hello Sir I Am 24 Years Old And Suffering From

Hello Sir
I am 24 years old and suffering from Brain Fog and continues wait loss since last 2 years.Brain fog/ Mental clarity increases at night time and espically I eat something spicy. I was used to have constipation since birth but now I am passing stools twice and sometimes thrice a day.The stool is sticky but didn't notice any blood in it. I had some tests done such as colonoscopy, endoscopy, ttg, blood count, thyroid, USG whole abdomen and all came negative.
3 GI diagnosed me with IBS. I am taking "Librax", "Vibact DS" and "clonofit beta" since 5 months. There is a slight improvement in my brain fog( still face lack of mental clarity) and fatigue but I am not able to gain weight( not even 1gm). My height is 6' ft and weight is 60 Kgs. It might be IBS but I think my GI are not working on the root cause of the problem. It can be anything such as SIBO, villi disturb, Candida Overgrowth or Leaky gut. One GI told me to go for Hydrogen breath test. I didn't get it done Though I took rifaximin(200mg thrice a day) for 10 days but didn't feel any improvement. I also tried to stop gluten for 15 days but there was no difference in my health. I also took ofloxacin and sompraz but didn't see any change. Also, I am not able to digest milk( but can easily digest curd and buttermilk). Please suggest me whether I should change my medicines or not. Also, are there any other tests( excluding the tests mentioned above) which I should consider.
Thanks in advance
Mohit Sachdeva