"Is God calling me to a religious vocation?" you ask. Dear sister in Christ, praise God! You are on your way to finding the answer to the deepest desire in your heart. But first, there is one thing God asks of you. He has given you the key to the eternal treasury which holds all that you are seeking. This key is your yes! Give your resounding yes as Mary gave her Fiat and God will unlock for you this priceless treasury.
Only months ago I was asking the same questions you are: "How does God want me to give Him my fiat?", "Is He calling me to religious life?" Among the many ways God filled me with strength to overcome my fears and honestly seek His will were the words of Jesus Christ re-echoed by John Paul II: "Do not be afraid!" Hold onto these words and remember that "perfect love casts out all fear."
Know also that your Heavenly Father gazes on you with a unique love just for you. He who created you, who "knit you in your mother's womb" wants to satisfy your deepest desires, which He knows. Do not put Him off any longer but seek wholeheartedly His will for in it is your eternal felicity.
Above all, I have one word for you. It is the Word made flesh, Jesus Christ. He calls to you and says, "Arise, my beloved, my beautiful one, and come." "Follow him eagerly" so that you may truly say, "My lover belongs to me, and I to him." All He asks is for your "Yes"!