What should you do if you think I've been drugged and raped?

Seek assistance. If one believes they have been drugged and raped, the first thing to do is get medical attention - maybe going immediately to an er for a rape kit to be performed. This may help answer the quesiton and important evidence may be gathered. Gathering anything the drug may have been in may also help with the forensics. In terms of trauma, asap speak to a rape crisis counselor or clinical psychologist.
Get to an ER Now. A pelvic exam will reveal if semen is present, and that can be used for DNA and STD testing. It's important to be as detailed as you can in describing the scenario as this will help the authorities. It's difficult to put yourself through this, but remember if you have been victimized, you are probably not the first or last person who has or will be hurt. Protect others as you get help for yourself.
Get to a hospital. If you suspect you have been given a drug, you need to get to a hospital to have your blood tested for these medications. These medications are usually short acting and do not stay in your body very long. Do not delay.
Depends. Do you know the person who administered the drug.? Were you in circumstances that point to your innocence? How soon after the event are you reporting this? Time is crucial for things like semen analysis. Is your goal to criminally punish the rapist, or tell the tale in some other way, or to seek revenge in some way. All of these things must be factored into a plan of action.