You might consider looking up a support group for moms that have lost children to miscarriage. Many times your OB/GYN can recommend one to you, and/or can recommend a counselor that specializes in this type of grief counseling.
It is unfair of those around you to ask you to get on with your life. To you this was more than a "fetus", this was your baby. You are going through a time of grief and bereavement just as real and deep as if you had held the child in you arms. And sometimes it is even harder, because you did not get that sense of completion - it is like you had to stop in the middle.
You are also grieving the fact that you may not be able to have children; I went through this when i had my hysterectomy. Everytime I saw a baby I felt empty and I would dream of empty cradles. This is not uncommon.
Explain these things to your family and friends. If they will not listen to you, then seek support elsewhere. You will be amazed at the difference it makes going to a support group though. Being with other women who say "I understand" is so refreshing! They understand when you cry, and they hold you up when you feel drained.
They will also let you know when your grief becomes dangerous, and when living your life needs to take priority over grieving the dead. But for a little while, it is perfectly normal and ok to let your heart go for this little one (ones) that you have lost. They were a part of you, no matter how long or short a period of time.
My prayers are with you.