I'm so sorry that your family and boyfriend are unable to be supportive. Sadly, there are many people in this world who do not understand the bond that one can have with a pet. But as you well know, this is their loss. Can you imagine what it would be like to go through life without knowing this kind of love?
I understand why you are concerned about a future with a boyfriend who is unable to be supportive when you are grieving so much. Grieving is already allowing you to grow and understand what is important to you in this life and maybe this is a gift from your baby girl. She is allowing you to see what you want in a significant other. Having said that, making a decision when you are grieving may not be a wise choice. Perhaps you can just back away for awhile and see what happens. I personally believe that men grieve differently than women do(not more, not less, just differently), but I do know for certain that I need a man who understands how much I am suffering wen I lose something this important.
If those around you do not offer support, you will find this site to be the support that you are looking for. Here it is safe to vent your anger, your uncertainty about your choice, your fears, your sadness, your loneliness. You have in a way found a loving, supportive, non judgmental family of sorts. When I first came here many years ago, I found so much help writing and reading all of the responses. My friends and family were supportive, but it was so helpful knowing that there were others out there who truly understood the depth of my grief. I didn't necessarily let family members and friends see that.
Thinking of you and your special girl.