Hi. We can continue after this if you'd like
My concern is the combination of the low blood pressure, high pulse combined with the arm pain. While the arm pain could simply be muscular or a nerve pinch, with your history I'd have to consider it cardiac first. Unless that blood pressure and heart rate are the norm for you, this could be dehydration or cardiac or both.
I can't stress the importance of your getting medical attention right away--either by getting in touch with your doctor or getting to A&E.
I'll be happy to continue to discuss this with you but I won't be altering my suggestions