Im the same with the N and M sounds. Mostly because that little "ehh" sound before pronouncing the letter or word. Well for my job at least, i have to spell out the word for security purposes so I have to say "N as in Nancy, M as in mom" but where I struggle is "e-e-e-ennnn as in nancy, e-e-ee-e-ehhhmmmm as in mom". the EH annunciation in the beginning. If this is your problem as well, I try to start of with a soft HUH sound. So it's Hennn as in nancy.