To be or not to be?

Do I have a right to be pissed off? I asked my current boyfriend about his ex (who he had cheated on me with a year and a half ago 🙄) and I just asked what had happened and why it happened...he supposedly told me everything, but after a bit of searching through the past I found out he completely lied to me about it. Do I have the right to be pissed or am I being a ‘crazy stalker girlfriend’?