Just keep smiling... And wait
You have to let go of that feeling...
Just wait it out, you'll be fine either way. Just know that you can trust your gut.
Don't be predictable, move things around be different places at different times, confuse the heck out if them :D
Collect evidence/proof and gather as much as you can before confronting the person with it.
Set a trap for them.
It has to be a trap that leaves no doubt of guilt.
You're welcome and good luck!
punch them in the stomach
it is friend, it is.
Who are you trying to prove it to?
And who is the one committing the acts?
You can't prove something like that to someone who is in denial and believes his own lies. Just dump him.
Turn around faster.