Getting comfortable with selling myself, social media, & calling attention to myself

Hello. I started a photography business a few years ago & gave myself the opportunity to go full-time last year starting in May 2019. Being a shy introvert, my first obstacle to overcome was attending networking events & giving short commercials (standing up in front of the group & providing 30 seconds to 1 minute of information about me & my business). I attended several meetings each week and practiced socializing & speaking. It’s definitely easier now & not so stressful. I’m now trying to build my audience through social media posts, blogs, etc. I signed up for a Facebook course to learn how to grow my audience & engage. One of the first steps was locating several local business groups that had my ideal clients as members. Then to be social and start producing/sharing content. For some reason, I not only find this exhausting but also scary because I’m putting myself out there in front of a whole bunch of strangers. Yesterday, was the first day I actually posted in the groups. It wasn’t a sales ad. It was just a Personal Branding tip. I couldn’t help but ask myself all the negative questions. Who am I to provide advice? Is my advice correct? Did I find all the grammar & spelling errors? Will I be laughed at? I’m working through this & now that these questions are crap & no one really thinks this way. But, I still wonder what my main reason for hesitation is. I don’t enjoy being the center of attention & I think this action somehow makes me feel this way. Can you please point me in the direction of learning more about how to pitch myself, my business, my service and be comfortable with it? Thank you!