Believe me we are only human right? I think most of us feel the same. We don't reply to sad posts then feel guilty for not offering our support.
Just the other day I was reading the one about "How do you know when its the right time to let go"? I got through 4 posts and couldn't read the rest through my tears, I was in a similiar situation in March with my dog.
Please don't beat yourself up about it , we come on here for help and to feel good but there is always someone worse off than you. Thats life.