Like you my SAD is noticeable to people around me. It is a terribly uncomfortable thing and unfortunately contributes to the mental anxiety also. Not only do you fear your anxious thoughts but also your physical anxiety symptoms. For me, whilst I am working towards tackling and controlling my anxious thoughts I am taking beta blockers to help with the physical side of things. They work by blocking the action of adrenaline on the heart, thus keeping heart rate and blood pressure under control. They don't completely eliminate the physical effects as their main use is not anxiety but they definitely do help! You should be able to get them prescribed via your GP or through an online prescription. The doctor will make sure it is safe for you to use them before prescribing as obviously someone with low blood pressure could have some dangerous side effects.
Hope this helps:)