possibly pregnant?

Hi,
I had my tubes tied 19mths ago after our lovely daughter and youngest suprise.  I am 37 years old. My periods are always 21days like clock work. I am now late for my 2nd period, I have had 3 faint pos hpts and then some neg ones too. Seen the doctor and they said my horomone level was very low, about too low to suggest pregnancy. The nurse called today and said if I don't get a period by valentines day which would be 3rd missed period that I need to do another blood test. My sister suggested that maybe the first month I didn't ovulate and then did ovulate the last time. My last period was Dec 16th...on Jan 15th I thought I had started my period just late. When I went to wipe there was a lil light pink on tissue.  I went through the normal of preparing for my period..which never came. I questioned perimenopause and they said very unlikely. I only missed periods in my life before when I was pregnant. I am tired, sore breast that have stingy tingling, nausea...craving ice..which I only did before when pregnant..I also have a huge vein that only bulges on my chest that runs to my breast..it has only every enlarged like this during pregnancy...Can I get thoughts from someone?? Please..it's driving me nuts