I recently read a beautiful book written by a woman who was given visions of heaven, as we would understand it to be. During these visions she saw a baby die and taken to heaven. What happened is special angels held the tiny soul in a special box and carried it with all speed to God. God Himself took the tiny soul from the box and formed it into the child that it was to be and gave it life. She was told that moms of lost babies (even those from abortion) were given the chance to raise their child in heaven. So the child was never "lost" but was "babysat" by the best baby sitter ever.
I hope you can take this idea and hold onto the belief that your baby is in heaven with God, waiting for you. S/he will be there when you reach the end of your life and you will be able to care for this little one that was lost so tragically. I hope I don't offend by saying such faith based things but, God can and will forgive you if you ask Him to! All He is waiting for is for you to go to His Son Jesus and say, "I am so very sorry that I made such a choice, please forgive me!" Before your prayer is even finished all will be forgotten and be as if it never happened. Jesus will teach you how to deal with the pain you feel from the abortion, just trust that He loves you and will do so.