Did it ever occur to you that God may well have been listening to your prayers all along, and has even been answering them—but His answer is "No"? This probably isn't what you want me to say—but it may be true.
After all, God knows all about us, and He also knows what is best for us. To put it another way, we see only a small part of the picture, but He sees the whole. He knows all about you, and he also knows all about this person and whether or not you would really be happy together. The worst possible thing you could do would be to marry someone who was not God's choice.
Sometimes God answers our prayers by saying "Yes," but sometimes He says "Wait" or even "No," and the reason is because He knows what is best for us. Often I've prayed for God to do something I thought was good but His answer has been "No." Only later did I realize how misguided my prayer had been, and how good God was to refuse to answer it the way I thought He should.
The most important thing I can tell you, however, is that God loves you—and because He loves you, you can trust your future into His hands. The Bible says, "It is God who ... makes my way perfect" (2 Samuel 22:33). If you have never done so, confess your sins to Him and ask Christ to come into your heart and take control of your life. Then trust Him to lead you to the one of His choice if it is His will for you to marry.