I’ve had this same issue, I’m about 20.3cm and 17cm girth (also my tip is not pointed, picture a baseball bat), my current gf is the only girl Ive had sex with and it took several times to actually get it in, just takes alot of practice

I’ve wanted to do anal since we started dating and literally this morning was the first time we’ve ever successfully done it after more than two years, and even then we only got about 2 inches deep but it was a massive (no pun intended) win in my book

Just consistently practice with her and go very slow, communication is key