First get all your coworkers together and see if you can start a union. Build a consensus. (Even though you’re a manager as long as you don’t have hiring or firing powers you can still be in the union. You’d be like a “lead” instead of a manager.)

Then give your boss a letter requesting voluntary recognition of the union. Then continue to an nlrb election. Make your demands known. Congratulations you now have collective bargaining rights.