JJ,
I promise not to judge you for your past choices and actions. I have never had an abortion, but I have had a couple of pregnancy scares when I was younger and I remember how terrified I felt at the prospect that I might be pregnant (luckily I was not pregnant). It doesn't seem uncommon for girls who have had abortions to feel lonely and empty and feel jealous of women with babies and a desire to be pregnant again.
While I won't judge you for the past I would encourage you to choose to have THIS baby. I can relate to fears about balancing grad school and pregnancy. I just started by grad program when I found out that I was pregnant (my husband is in grad school too!) It hasn't been too bad being pregnant and in grad school....we'll see how next semester goes when the baby is here! I do not currently and I doubt that I ever will regret having this little boy.
At least you have a loving fiance who will be a supportive husband and father. Perhaps your family would be upset about an unplanned pregnancy before you are married, but if you are moving in together before you are married they have probably figured out that you two would be sleeping together. They might be upset at first but they could surprise you and turn out to be more supportive than you might have anticipated. If finances are an issue there are resources out there to help. Also adoption could be a potential good choice. This way your child would be given a chance at life and you could focus on your degree and relationship and wait until you and your fiance are more ready to raise children yourselves. You could choose open adoption or closed adoption.
I understand the dillema your facing and that this is not an easy choice, but I do hope that you do not choose to have another abortion. I hope that you do decide to have this baby - whether you raise the baby yourself ar give it up for adoption. Best wishes.
Kate