You know, when Abraham was asked to lay down his beloved son Isaac (his long-awaited dream!) on the altar as a sacrifice, God did not ask him to stop loving his son.  No, God was merely testing him and asking Abraham to be obedient—to have faith and to follow his instructions for his life (Genesis 22).  Did Abraham want to obey God more than he wanted to cling to his precious child?  Amazingly, yes.  And he did it without hesitation.  Abraham still loved his son (that didn't change!), but he gave back to God what God had given to him.

Well, it took me about six months before I would finally let go of my dream.  I agonized and cried and probably figuratively kicked my feet like a little child.  This was MY dream, and I had become obsessed with reaching it because it was what I desired for my life

But after a time in the depths of despair, I realized that I would never be happy and fulfilled unless I gave this dream to God.  When I did, he showed me that I could still have this dream (and that it was from him) but that it had to be repositioned in my life.  I could still appreciate it, but it needed to be in the proper place so that the primary desire of my heart would be in line with what God wanted for me.

And that, I think, is the real crux of matter:  we must desire to do what God desires us to do.

I desire to do your will, O my God; your law is within my heart (Psalm 40.8).

That means obedience.  When I obey the Lord, the desire of my heart will naturally fall in line with what his desire is for my life.  Sure, it’s easier said than done (how many times have I said that?).  But I know that God can change the desires of our hearts to conform to his

Delight yourself in the LORD and he will give you the desires of your heart (Psalm 37:4).

It sounds like you may have come to a similar place.  Perhaps you have made peace with God regarding not becoming a parent.  He has shown you that this is not his plan for your life.  And if that is the case, then I believe you will find contentment without having a child (and only God can help you reach this point). 

But he also may be asking you to just put your dream to the side for the time being, so that he may open your life to other opportunities or another desire that he wants to place on your heart. 

Also, I know plenty of couples who married “later in life,” beyond the childbearing years, and the Lord has blessed their lives—even without children.  They are still being used for God’s purposes, as they serve him through the union of marriage. 

And then there is always adoption.  You could meet the man of your dreams tomorrow, get married and then decide to adopt a child.  Or perhaps the Lord will steer your “parenting dream” toward working with children in some capacity (serving in the nursery at church, volunteering in an after-school program, leading a Bible study for young girls, babysitting for your nieces and nephews or friends’ children, etc.).

I know how you feel.  Believe me.  As you said, you feel “so lost and so alone” right now and are having trouble as you focus on the limited options you see around you.  But look up!  And keep your focus on what you cannot see as you surrender your heart to the Lord.  He has a plan for you (he makes the options possible, so they are limitless!), and he knows the dream you have been carrying. 

In his time, I believe he will show you what he wants to do in your life as he works in your heart.  Have faith, knowing that trusting and worshipping the Lord comes with a cost as we offer ourselves (and our dreams!) as a sacrifice to him.  But know that the Lord WILL provide for you as he sees best.