I think I have been knitting the wrong way :( Sigh...
I watched all the videos here and I knit differently than the regular knit st.
Instead of inserting the needle under the front yarn, to the back, yarning from back to front, I insert the need in between the yarns (middle of the stitch) and yarn from front to back. Does that make sense?
My final result is the same. But yesterday I was trying to do the kfb increase for the first time and it is just a loose loop that won't become a second stitch.
So, I watched again the knit st video (and the kfb) today and I was doing wrong all along.
How did this happen?