Yes! Like you said it's from straining and blocking, when I get stuck I hold my breath - it's like my mouth and lungs go on a brief lock down and get light-headed when I can breathe again. I don't think holding your breath will have any major affects on your health, people hold their breath for swimming and what not so idk haha Other than that it's not great in terms of speaking, very tiring and also kinda scary. I'm sure there are techniques on how to get around this habit that someone will comment, from personal experience it involves just remembering to stop and breathe rather than struggle through the block