Your mum couldn't possibly know from changing your nappy when you're a baby how your dick is when you're fully grown. I'm also a little uncomfortable at the mum putting her hand on the bulge and asking to see it. There's a stage at the start of puberty were mothers kinda loos their free access to their children's nakedness, and it becomes something that isn't necessarily unhealthy or bad, but has to have the consent of both parent and child from that time on. For either side to force it against the other's will is innappropriate.

My dad did once follow me into the toilets at a restaurant to sneak a peek. He stood at the urinal beside me, and i noticed in my periferal (spelling?) vision that he glanced down to see. He then coughed, and moved 3 or 4 urinals away very quickly!