I just have a question regarding the necessity of ghusl in the below situation.

I woke up and got started on my day. my wife was fixing the bed sheets and she said that there is a stain on the sheets on my side of the bed which she believes is sperm which was not there the night before. I don’t recall having a wet dream and when I woke up I didn’t consider that I had one and the signs of ejaculation were not prevalent to me. I now have a doubt as to whether I ejaculated in my sleep or not due to what my wife has said about the sheets.

Is ghusl janabah obligatory on me in the above case?