Is it OK for me to use a pen name?

Apparently, yes. I’ve done some quick research here and here, and it appears this is done frequently (Mark Twain, J.D. Robb, many others). Authors may use pen names without telling anyone except their publishers (or Amazon, or anyone who needs to send you checks!) and if you’re self-publishing, well, no-brainer. Talk to a lawyer if you have any lingering questions. I am not a lawyer, and anything I say about pen names should not be taken as authoritative.