It sounds odd. You don't acknowledge these imaginary friends around others do you? What you do alone is your business. At least we jmo you're not SZ. Cause after talking to yourself for so long.. hey do your imaginary friends have different personalities?
As long as you acknowledge they're not real, and they're not causing you any problems, then there's no need to seek out any help unless you really want to.
Don't worry, you're fine. :)
"The only normal people are the ones you don't know very well."