I'm so glad you asked this. I have to say I'm a little too shy too ask such things, but I have the same 'problem'. I love deep throathing, although I'm not experienced and my Master takes it slow also, but every time I do it, my throat feels soar and swollen. As if I had a cold.
And when He has cum, it is even worse.
I'm sorry I can't help you, but I'm glad I see I'm not (the usual) 'only one'.