Gettting caught measuring your penis

it was 1992 I was 17 and my girl friend at the time saved my cock and balls, she loved to measure my cock so the day she got It cleaned up I went home and ate and then took a shower, when done I went to my room and took off the towel and set on the edge of the bed. I had a wooden ruler, under my bed, so I start jerking off to get hard and it does so I lay my cock on the ruler and the bed room door opens and my mom said what are you doing I dropped the ruler and in embarrassment I said on the guys at school told me to do it which was a lie I was doing to tell my girlfriend when I called her. well I was sitting naked with a hard on and mom stood in the door kinda laughing and walks over and I am about to cry she picks up the ruler and said you lost some of you erection so get it back I want to see how big too. I didn't know what to do so I pulled it about 5 times and it was full erect, she still has the ruler she leans over and puts it between my legs and grabs my dick and puts it on the ruler and says 7 and 3/4, I was still uncomfortable, she hands me the ruler and says you have a nice dick ##### (my name) and walks out and nothing like that ever happened again.