Stutter when I think what I want to say but usually talks fluent

Stutter when I think what I want to say but usually talks fluent Hi there, hope everyone feeling well! I've been a stutterer myself from a young age but It was not severe but as I grow older it became a thing like one time i was in a class and was trying to mark attendance for my friend when his roll number called I was not able to say the roll number even the whole time I was sure that I could say it but wasn't able to at the last moment so I don't noe whether it is confidence issue anxiety nervousness or stuttering. Someday I felt very confident and not even a single stutter occurs someday I feel like I dont have the energy to talk and whenever I try to talk i feel like im suffocating and unable to breath and cant get the word out also my head gets dizzy. But here's the thing im in graduation and whenever I gave presentation I would speak normally or stutter a little bit but when I overthink what I want to say that where the block start to appear and make me unable to speak I also have a problem that at some words when I try to say them indivually i just get blocked like all my breathing just stops but when I say the exact same word with other words or with a flow they came out perfectly.