pins on nipples, male

[Naddy3]

I love to put at least two bobby pins on my nipples. sometimes more. It make them in constant state of arousal. If the sensation slow, I just push or pull the pins on tighter or add more. To the point that my nipples really hurt til then get accustomed, then I push/pull more.
My wifey is so prudish and would never understand this.
The problem is from time to time I wil 'looose' on or more of these and don't realize it. then she might find it...as she has from time to time and will say something like: wadda you do with these pins? where did this pin come from? heres another of your pins, wadda u do with them?
so...what else cud I use on my nipple at would not fall off. Would not be really painful to wear (like stiff clamps), and would not be suspicious if she found/saw on on the floor???