I'm sorry to hear that this happened! Many times, it is possible to reach up into the vagina with your fingers and extract the condom yourself. It is sometimes easier to ask your husband to do this for you. However, if neither of these strategies is successful, then you should go see your primary care doctor
, or your ob gyn doctor, right away. They will be able to extract the condom very quickly using a long handled pair of tweezers or similar medical instrument, and it shouldn't hurt at all. It is also important to get this done right away, because objects left inside the vagina may be a source of infection, or they may cause irritation of the vaginal wall.
Another thing that will be important to discuss with your doctor is the potential of a becoming pregnant. When the condom slips off inside the vagina, the sperm can get out and can lead to a pregnancy. You are, fortunately, still within the window for effectively using a "Plan B" type emergency contraceptive medication. Your doctor will be able to prescribe this medication to you if you wish.
Call and make an appointment with your doctor right away to be evaluated.