Yes. Statistically speaking there has to be other life out there. And everywhere we thought there wouldn't be life, there has been.
And yes to aliens being here already. Maybe not in the classical bipedal alien sense, but some sort of interdimensional life. I've seen balls of light in the sky on more than one occasion, and pretty sure it wasn't ball lightning (seeing that once is rare in itself).. they phased in and phased out, and sometimes zigzaged a bit.. and these events happened on days when I was very heightened emotionally. I also got the sense that either I could feel when these things were about to appear, or perhaps they could sense my mood and thoughts and appeared at very 'coincidental' times in my train of thoughts. Very odd experiences.
I also believe entities play a much more fundamental role in human psychology and humanity than we currently realize. Not in the sense of Icke's reptilian theory or any grand cosmic conspiracy, but more along the lines of they're another class of life/species, some of which is friendly to us and some of which treat us as we treat cattle.