Frequent Headache, Tightness In Neck, Heavy Heart Beat In The Painful Part Of Head, Low BP And Pulse Rate. Suggestion?

I ve had headaches for 31 yrs, they have gradually become more frequent, so that in the last 5 yrs or so I have at least one every two days (more troublesome in the winter than summer). Headache pain is no longer confined to the right or left hemisphere, now it can be most anywhere in the head. Pain is fairly mild when the HA starts, taking 4 - 6 hrs to most painful, and lasts 12 - 16 hrs (sometimes 30+ hrs). Only 2 - 4% of the headaches are as painful as they were in the early yrs. I m experiencing pressure (tightness) mostly in my neck and head accompanied by heavy (hard) heart-beat occurring in the the most painful part of the headache. The pressure (tightness) is a dead ringer for that experienced when taking Imitrex . With the last few headaches I can feel and hear the heart beat plainly and notice it is skipping a beat (4 beats then a miss). I have low blood pressure (100 over 70), pulse 58 to low 60 s. I have seen all kinds of doctors. I ve tried just about everything but acupuncture and botox. Began taking allergy shots 2 mos ago, hoping that may be the cause as I did have HA and vomiting as a kid and took shots which greatly relieved that problem. Oh yes I m 69 yrs old.