I showered with my MIL (58)

I'll try to keep this short but I wanted to share it with you all because it happened quite recently.

My wife (25) and I (27) have been happily married for over a year now.

Her parents live quite far away, so whenever we visit we stay for a few days.

Last weekend we stayed over as well, as it was my sister in law's birthday on Saturday.

We had a great time.

On Sunday morning, we decide to take it easy and my wife asked me to join her in the bath. We don't have a bath in our house, so we both get in an have a relaxing time. After a while, we're done and my wife gets out of the bath first and steps in the shower right across from the bath to clean herself off. It's a small shower and it doesn't fit both of us, so I stay in the bath a little longer. When she's finished, she dries off and leaves the bathroom, as I get out of the bath and get in the shower.

At this point, I hear the door opening again. The bathroom has a weird layout,it looks like this, so I can't see who it is. I assume its my wife and that's she's forgotten something and think little of it. Half a minute later, I suddenly see my MIL completely naked coming from around the corner. I don't know what to say so just quickly grab my junk not to expose myself. She tells me that she didn't realize I was still there. I apologize as well and tell her that I'll be done really soon and that I'll hurry up. At this point I still have shampoo in my hair. My MIL however, does not wait around the corner where I cant see her, but instead decides to get into the bathtub. She tells me it would be a waste of water not to enjoy it as well. I can't help but stare at her body as she gets in. But then I suddenly realize that she's now fully submerged in the water, while she has a clear view of my naked body right in front of her. My mind is racing and I don't know what to do, except shower faster than I ever showered before. She keeps talking to me about random stuff, while I do my best not to get hard or look at her too much, even though she's right across from me.

After hastily drying myself off, I head back to my wife's childhood bedroom to get dressed. The whole ordeal took roughly two minutes I think, but it felt like hours. I'm now in a really confused state. I never thought about my MIL in any sexual way, but I can't unsee what I saw. Something inside of me now wants to see more. I knew that my wife's family was pretty easygoing when it came to nudity, but I was still not prepared for this. So many things are going through my head right now, I just wanted to share it and write it down.