Missing so much

I was just told that my 11 month old niece is now walking.  I love her and am so happy but this just reminds me of all the stuff I will never get to see my son do.  I wonder what he would be doing now at 8 months.  I always picture him as a funny little guy like his father, laughing and smiling.  This is the worst pain, why do we have to go through this?  Really?  It took 4 years to conceive my son and he passes one day before he was due.  What have I done to deserve this much pain?  I miss him so much, I will never be the same, life will never be the same.