I suspect some of it is simply being a new mom, and some of it is having a history of miscarriages. I would consider doing the following things:
1) Join a group that deals with miscarriages. This may help deal with your losses and fears.
2) Join a mom's group with a general focus (not focused on loss). This may help provide support and help you develop a different mindset.
3) Sign up for an exercise class.
4) Learn a new instrument or something else new.
5) Do some volunteer work.
6) Take on a part-time job (if you're not already working).
Basically, the point is to change your pattern and expand your horizons beyond your current situation. You can bring your daughter along with you to some of these things or make arrangements for her to be safe somewhere.
When I have an opportunity to think too much, I can get myself into some crazy cycles of thinking. I don't mean to keep yourself so busy that you don't do any reflecting at all. But expanding your life experiences to more than just you and your new bundle of joy can be very therapeutic.
If none of these things (choose one or two or so) seem to help, then I would consider if therapy would help. Counseling can provide a healthy perspective in the times when we forget to keep our own balance. It is a sign of strength to know when you need outside help and when you don't.
My best to you. I suspect having lost two babies, you are delighted to have your new daughter and fearful of any additional losses. That in itself can be a delightful and stressful endeavor!
Peace to you!
S. : )