Selecting Multiple Lines Of Text?

I usually click and drag straight downwards to select paragraphs or multiple lines of text in my browser or word.Now I can only select a few lines before the text gets unselected and then it starts selecting text farther down where mty cursor is. Or if I drag too fast, the entire selection gets unselected. I also noticed that when I double click on a word or sentence, the whole word or sentence gets selected. If I drag veeery slowly downwards from left to right, I can manage to select a little more text than I would have if I did it at the normal speed