nauseous after swallowing

basically i wanna know if anyone else feels nauseous to the point where they need to vomit after giving head and swallowing? ive done it around 3 times and every one of those times i've felt nauseous and my stomach felt all bubbly.. ever since then, i've just let him do it on my body instead of me swallowing, but he prefers me to swallow... 
is there any way of swallowing and not feeling sick etc. ?