Constipation since 1 year after bells pa

I have constipation problem since last one year when I had bells palsy paralyse. I have done all test which were negative CBC,throid,iron,lipid,ultrasound,lft,kft,urine,rbs etc and Endoscopy also negative. My current medicine BIO d3 strong at night,nexnuron after dinner,petril MD 0.5 bed time,Prothiaden 50mg three times a day, lactic fiber(lactitol monohydrate 10mg, isabgol 3.5 mg in every 15mg.), pan it two times empty stomach in morning and evening. My gastro doctor says behcets disease and refer skin doctor. Skin doctor says I.b.s. he first add one syrup  cremaffin at night with isbgol which not work. Then he prescribe dulcoflex 5 mg withisabgol which also not clear my stomach. Is it a problem gastrologist or psychiatrst. I have also shown every doctor neurologist,psychiatrisrt endocrologist, diabetologist,cardiologist, dermatologist, ent doctors