The only person you should be comparing yourself to is yourself.
You're not even aa junior yet, so chill. You have plenty of time.
This past year, I felt very overwhelmed with classes and stuck to just Autism Speaks. This is one of the reasons why I now feel so unqualified as I'm comparing myself to some of the other posts on this forum.
It's not too late. Don't try to do everything at once. Good time mgt is a crucial survival skill for med school.
I have no research experience, no clinical experience, no shadowing hours yet. I really want to start hitting those areas hard this summer and continue into my upcoming year. My fear is: is it too late?
You do need to work on the self-esteem. In the worst case scenario, you do a gap year and have a nice app for the app cycle after that.
Should I consider a different career path now, or will it be possible to change my lacking of extracurriculars enough to be competitive?
You should start shadowing and doing some clinical volunteering. Save research for SR year. Your desire to work with this patient population is admirable, but you need to show Adcoms that you know what you're getting into, and that you really want to be around sick people and their families for the next 40 years.
Should I focus on particular areas such as clinical experience, or try to cover everything? I enjoy working with kids on the spectrum and am hoping to do more for them this year.