Why is my pubic bone so large? i understand im decently overweight (510 220pounds) but its to the point where my penile shaft is hidden & it really affects my mental health since my penis never really grew in the first place during puberty. im 20?

The choice is yours: Without more descriptive information we cannot assume your penis did not develop/grow. You just have extra weight that often makes it appear that way. Discuss this with your doc. If they can get you help loosing weight & it will improve things overall. This is not an unusual concern. I have heard it from kids as early as age 12, when they become more concerned with body image.