I'm 43 and just missed my period. I had all the pms symptoms but never started. I still am having breast tenderness. Could it be perimenopause?

Mmm have you been having sex? Even at 43 you could be pregnant unless there has been no sex.

Its possible to start menopause in your 40s however, so I would say speak to your doctor, as both possibilitys should be dealt with right away.