You need to take a test. While it's normal for young girls to miss periods or have changes in their cycle, the fact you have had sex warrants the need for you to have a pregnancy test. It might also be a good idea to be tested for STD's just in case. Being as you were drunk you can't be 100% on what happened. Better safe than sorry! Good luck!
I would take a test. If it comes up negative then call your doctor. I am not sure how old you are but if you are a teenager sometimes your periods can be off or not come at all because your body has not regulated itself yet. But if you haven't had your period in 3 months then you really need to take a test. Get an appt if it comes up negative. They may want to do blood work like a blood hcg level and hormone levels. Good luck.
Have you gone to a doctor, or taken a pregnancy test? If you say that you're drunk heaven only knows what actually happened.