First off, I encourage you, if you desire to marry and to bear children, to earnestly present that request before the LORD. He knows your heart and your passions. He does not tire from hearing your will. But you must trust Him as you wait for His answer- and delight yourself in Him as you wait.
Psalm 34:7 says, "Take delight in the LORD, and he will give you the desires of your heart." Delight in His goodness and His grace. Delight in the way he provides for you and is intimate with your heart. Delight in the knowledge that He has a great love for you and will do what is best for you.
This is not always easy. Ross and I dated for a long time (considering the amount of time we had known each other prior to dating and the certainty which we felt about our relationship.) There were many evenings where I cried to God- asking Him why we weren't married already. Why He wasn't following my plan.... Patience and reliance is not easy, but critical to the Christian walk.
Secondly, I urge you to use your singleness for His glory! There are so many things that you are free to do that us married ladies are not. You don't have to worry about getting dinner on the table, or being home for nap time. You can pursue exciting missionary endeavors without having to worry about leaving your family at home. I encourage single women to do exciting things for Jesus- to spend your time blessing others, instead of pouting over the marriage you don't have.
Finally, I ask that you apply the principles of Biblical womanhood, found in Titus 2, to your lives as well. You may not have husbands and children, but that doesn't mean you can't support your girlfriends that do. When a friend of yours complains about her husband, gently remind her that you would love to have one yourself and that it is best for her to enjoy the man God has given to her. Delight yourself in other people's children. Teach and guide them to love Jesus with all their hearts.
Honor your bodies and the holiness of marriage by keeping yourself self-controlled and pure. Bless others by using your gifts of hospitality. Shower others with kindness.
Remember how we do all of these things so that the gospel might be proclaimed? Think of the beautiful picture that is presented by a single woman who doesn't complain about her singleness, but rather uses it to glorify God and to edify the body of Christ! A woman who is gracious and kind, hospitable, caring and pure is a lovely display of the gospel.
Do not be ashamed of your singleness, but rather embrace it as an opportunity to love the LORD and be a blessing to His people.