Is It Normal For A Boy To See His Mom Nude?

I am a boy aged 22 and my mom is aged 45. Recently we moved to a new house and my dad remained in the old city due to office work. As we moved to a new place, my mom asked me to sleep with her. The initial days went fine but one day I woke up to drink water. Then what I saw was really shocking. Her pussy was fully exposed in front of me. She was wearing a simple maxi nightdress which rolled up while she was asleep. Maybe she won't have the habit of wearing any inners while sleeping. As she was in deep sleep, I didn't disturb her and so went to sleep.

Another thing I noticed is that my dick got erect and hard the moment I saw her in that condition. I didn't ever think of her sexually any day and that all happened in the blink of a second.

The same happened the next night, as her dress rolled up and her pussy along with buttocks were exposed. I dick got hard again but I felt guilty about it later. The thing learned is that she dont have the habit of wearing panties while sleeping.

I can't say her directly about the matter and she also dont have any idea about it. I do feel guilty about it.
Well, am I wrong in this situation? As I really dont know as all happened real quick.