So sorry to hear that you have lost your husband.
What you are going through sounds quite normal to me.
And yes, I have experienced something similar to the feeling or whatever we should call it that you have had and I fully understand why it has upset you.
10 years ago, my sister and I went back to Scotland where we had grown up for the first time in nearly 40 years. Whilst we were there, I woke up one morning completely convinced that my adult life as I had lived it up to that day was a dream or a hallucination and that there was no DH waiting at home in Copenhagen, that I didn't have a home there, that I had never left Glasgow and that I would have to try and find my life in Glasgow.
In short, I woke up, convinced that I was suffering from a form of amnesia and that the memories I had were all a form of madness.
It hasn't happened again, thankfully, and it only lasted a few minutes, but I found it horribly unsettling.
I hope your similar experience soon will be a thing of the past, your husband did live and you have 52 years to look back on once you get past these first difficult months where you weep every time you think of him and all that you had.
The only positive thing to be said is, that it is generally said to be healthier to be able to mourn just after a death, than not to be able to. It is very early days yet, so please do take your time. Feeling guilty about this and that is part of the process, but perhaps something one should try not to do, as probably you have nothing to feel guilty about.