When you say that oral sex is wrong you need to provide some basis for your “opinion” and not simply state that it is wrong.
Oral sex/stimulation is allowed within the marital embrace as long as it is not degrading to either spouse and the act ends with the husband climaxing (ejaculating) inside of his wife’s vagina.
We must keep in mind that the act must be both unitive (uniting the husband and wife in a renewal of their vows) and procreative (open to new life)
Please take the time to read “The Good News About Sex & Marriage” by Christopher West and this will do wonders for you to answer your questions.
Bear in mind that in asking this question you are going to subject yourself to many, many different opinions. Some will find any type of oral sex offensive and will say that it is wrong. The truth to that is that if it is an isolated act not ending in the husband’s orgasm inside his wife it is sinful.
Oral sex or oral stimulation used as foreplay is not a sinful act so long as you complete the act inside of your wife’s vagina.