Attorney Problem/Auto Accident

i live in st. louis, missouri. on june 10, 2000 my girlfriend and i were passengers in my sisters car when she collided with another vehicle (rented truck, explorer). now i contacted an attorney and at that time authorized him to handle the case. he sent my girlfriend and i to the chiropractor in which i assume he sends all of his clients. the last thing that i heard from the attorney is that the rental car agency insurance company is claiming their driver was not at fault. ok fine so my question is, should'nt my attorney now go after my sisters insurance company. my girlfriend and i were passengers and we have completed chiropractor sessions (over 8 months ago) and i believe we should have been offered a settlement amount by now. we have not heard a peep from the attorney and it has been 1 year and 4 months. i would like to have another attorney assigned to the case is that possible? help.