i love you so much
It is Spanish for "I think I love you". Also, creo is used more in line with believe. As in, "I believe I love you". Pienso is used more to mean I think. In this example, pienso is "less certain"...
Most likely, it means: 'how I love you.' Though it could also mean 'that I love you,' if it were part of a larger sentence.
i love you more than you know
It means I love you so much my love