Talk to Speech Therapist on Facing Speech Difficulty, Stammering/stuttering And Blocks While Speaking

Respected Doctor, I am facing difficulty while speaking. I experience speech blocks, stammering (atkan), and trouble pronouncing words smoothly. Sometimes I feel unable to get words out at all, especially during conversation or stressful situations. Please guide me: Which specialist doctor or Speech Therapist / Speech-Language Pathologist (SLP) should I consult for this issue? Are there any initial tests, evaluations, or speech therapy exercises recommended for diagnosis? Thank you.