I've been there Eileen.
I can tell you that it never goes away, you just learn how to better cope with it. Every year, on the day I estimated would of been the birth date, I conduct a very private ceremony in memory of the baby, its father and acceptance of the circumstances that led to my decision. This year was the 30th. I do it on the birth date rather then the abortion date because I prefer to remember that date rather then the other.
Now and then when I get familiar with a young person I'll sometimes catch myself thinking "hey, this person is the same age my baby would be right now" and sometimes form a maternal bond with them. During that ceremony I mentioned, I spend some time fantasizing about what the baby's life would be like and how different, for both good and bad reasons, my own life would be if I'd made a different choice.
I have a few regrets, not for the baby, but for my family. My parents never became grandparents, and on my mom's side of the family my brother and I and a cousin are the last of the line. Neither my brother nor I have children to carry on the history. That is a big regret for me now that I am beyond childbearing years.
Knowing then what I know now, would I have made a different choice? No. There were too many complications, and even though I married the baby's father soon after, our marriage only survived 3 years.
One thing I am very thankful for is Roe vs. Wade. My abortion occurred very soon after the Supreme Court decision. I had medically safe options available rather then backstreet hacks.
Eileen, go ahead and grieve if you feel the need to. Find someone you feel comfortable talking with and share your feelings with them. Eventually, when the distance of time has taught you to better cope with your feelings, create your own memory ceremony and allow yourself to grieve on that day if you have the need.
Giving yourself a day to remember will help cope for the other days of the year. You've got a long life ahead of you. Don't let this stifle the possibilities. Embrace it, but don't obsess over it.
If you'd like to communicate privately with me, let me know and I'll give you my email address.