JamesR,
Personally, I have always wanted to be a father, even from a young age. I was excited to get married and now that I have two wonderful, amazing, but trying and challenging handfuls, I am more and more blessed. Marriage is a martyrdom, over and over and over. Now, as a parent, I can understand why someone would not want to get married, but it is a tad out of the ordinary to desire marriage, but seek to intentionally frustrate one of the greatest fruits of the blessed union which God joins together. Children are a blessing for many reasons, but one of the hardest lessons one learns as a parent is the blessing and Grace God grants us because of the "burden"/"frustration"/"trials" from raising children. Raising your own flesh and blood, one who looks to you, mimics you, depends on you, seeks your love, approval, comfort, guidance...There is so much to say, so much to share on this subject. I honestly would say that perhaps you might consider the touch of immaturity that within the idea of being married, but not having children. In this way, I agree with what has been said that you should speak with your priest. Also, try and consider the endless possibilities other than avoiding children. Being married, there are bills, friends, jobs, Church, social life, personal hobbies, crafts, growing in love and patience with one's spouse. There is hardly time to implement a "controlling reproductive regimen" into your new life that won't cause significant spiritual damage. If you have an honest and sincere medical condition or something along these lines (or your spouse), then oikonimia would certainly apply, as long as you are doing so with the guidance of your spiritual father, but even then, you don't become immune to the spiritual damage that birth control causes.