Hoy can I do get a birthcertificate IF I Was never regesterd were I was born

That depends on what country you was born in as that's where the documentation would originate from.

I was born in mexico my mom is american I have 23 Years here in Florida

If you was born in Mexico.. then any documents have to be originated from Mexico .. hopefully someone here will be familiar with how one would do this in Mexico. This can be very complicated even here.

Citizenship doesn't come into play as far as getting the paperwork.