A little confused

I was supposed to start my period on July 22 I had some cramping a couple days prior. I thought I was going to start, but I didn’t. July 22 came and went as the days went by no period, so I decided to take a pregnancy test and it was negative. As the days went by no period I started to notice some symptoms, such as tired and lack of energy. I have taken more pregnancy test and they are all negative. Now I am 18 days late still no period and all negative tests. I am starting to take naps during the day which I never do and breast are starting to be tenderness and another thing I am getting heartburn. I am not to sure what does this means I am only 45 years of age and shouldn’t be going through menopause. What should I do?