Baby fell!!!

I fell asleep with my 2 month old on my chest. Apparently, I rolled over in my sleep and he fell off!!! I truly feel like the shittiest mother ever right now. I let him sleep on my chest cause he doesn't sleep in his bassinet and, this way, we both get some sleep. I honestly had no idea I was that tired (I didn't feel that tired) and I am absolutely devastated. I watched baby for 2 hours after the incident and he seemed fine. He went back to sleep after I consoled him, and when I woke him up to feed again

he was in good spirits, smiling at me like always. I have no memory of him falling off or anything. My husband, who is absolutely LIVID with me at the moment, told me what happened. I have truly never felt like such a shitty human being. I don't know what to do right now....

EDIT: Thank you all for the kind words. I feel a little better and I'm just ready to put this nightmare behind me. I'm definitely going to be more cautious than ever now. Also, just to clarify, my husband was not watching me when this happened. He was asleep and woke up when he heard the baby crying and saw him on the floor, then he woke me up. Sorry for the confusion.