well why have you made an appt? - you must know what you want to ask! 
In a way, there is no need for you to see your GP. peri meno is not an illness.
Sorry to tell you but peri meno can last 10 years. Not in everyone, but the dwindle of hormones can last for along time and TBH if you have just missed 1 period, I don't know what you hope the dr to do or say.
She will tell you to keep a diary of periods, and if they stop altogether before you are 45, then you should consider HRT to protect your bones.
she might also offer you HRT if your peri symptoms become unbearable so that your quality of life suffers- due to flushes, sweats , insomnia etc etc.
But there is a HUGE amount you can do with lifestyle changes to help these peri symptoms.
my gynae has written a meno book - You change Your Choice, which is 50% conventional medicine and the rest complimentary -lifestyle advice- well worth a read.