Hi Olijoy, so sorry to hear your news. It's just absolutely gutting when you get the confirmation of what you suspect, even though in the back of your mind you think just maybe there is still a chance.
You really need to take time out to grieve and to do things you enjoy. Go and have a facial or do something for you, it is a good distraction.
In regard to why, my specialist said that the embryo just decides for itself whether to stick just like it decides whether it'll be a boy or girl if it does stick. There is absolutely NOTHING you could have done, it's out of your control.
Perhaps your chance will be with a frozen transfer - they say that sometimes the more 'natural' cycle, without the drugs, can be quite successful!
Don't lose hope, there are options out there for you. Thinking of you