I am so very sorry for your loss.  Sending healing hugs and prayers your way. People grieve in different ways, some need to fill the hole immediately, others like me took a long time to heal enough to even think about getting another yorkie.  I do suggest that you open up and talk with your bf about the loss -- if you posted the circumstance surrounding the loss, I missed it.  You are 100% right, you will never ever be able to replace your little Lexi, but another bit of fluff-love and puppy kisses will help you to laugh and laughter will help heal the hole in your heart.
 
again.... 

 and 

 headed your way