I like YLI hand quilting thread - it usually behaves better for me. I stopped using Coats and Clarks when I found thin spots and knots a few years ago.
Like the other poster suggested, try knotting the other end of the thread - I usually knot the end I just cut off the spool. You can also try using Thread Heaven to keep knotting down, just don't do what I did and get Thread Heaven on your fingers. I couldn't get a grip on the needle, LOL.
Janet