Dear Nolan, 

The only way you can tell if your inclination towards a vocation is a prideful thought is by examining your conscience, because pride is in us as an attitude and disposition we have. But you are going to have to go beyond that to answer the vocation question, for there is a difference between our attitude and God's will, and knowing one does not determine the other. This is beginning to sound like a riddle so let me say it another way. 

Your inclination towards a vocation may be a prideful thought, and yet God might still be calling you. You would simply be desiring the right thing for the wrong reason. Conversely it is possible that God really is calling a person who is leaning away from a vocation out of false humility. Of course the trick is to do the right thing for the right reason. How do you do that? By trying to get to the bottom line of what a vocation is. 

Vocation is what God is calling you to do. To answer a vocation properly you have to put him, his will and his example, at the center. You may be proud and think you are worthy of the priesthood, or have great ambitions of future glory... but look at the priesthood of Christ: service, work, persecution, betrayal, death, and only afterwards the resurrection. Are you willing to follow him under those conditions? By praying and putting his example at the center you can purify yourself of your pride, or if you can't get rid of it completely (the most common case) you can at least curb it out of love for him.  

Hope that helps. God bless.