Is there any way I can block MY number from showing up in a text??

Nope. Sorry.

Don't text people with whom you do not want to share your phone number.

Wirelessly posted (9520; (I'm mobile))

x2

The reason is that most people who want to do this are either spammers (dirty dirty spammers) or stalkers. There is no practical reason to do this, so it's never been a feature. In fact I don't think any phone will allow this.