Is it okay that I'm an adult and I still have imaginary friends?
Why would you still need imaginary friends?
I am lonely
You need to be more realistic about your life and try to make friends with real people. It is healthier to have real life relationships. Get involved in some group activities so you can meet some people your own age.
I'm just being me and no one is really getting hurt. It's my mind, my business and I should be allowed to do it.
That's definitely true, that it's your life and you're not harming anything by doing this despite it being a little strange. But don't you want to have a relationship with another human and interact? You may be missing out on great things, but to start then, how about adopting a dog?