A warm welcome to Mac-Forums, Ieda.
I'm going to suggest the obvious first, so please don't be offended.
On your keyboard, check that the Capitals key is not turned on. On most keyboards, this is found; far left, three rows up from the spacebar and usually there is a tiny illumination indicating that it is activated.
If that is not the cause, reboot the Mac. Amazing what that can solve. Then, perhaps, post back please.
Ian