You're definitely not alone.
I'm a 32 year old male who has always felt really confident, with a kind of "nothing bothers me" attitude - I've always liked to be the one that people can depend on.
Anyway, 6 months ago I thought I was having a heart attack and called myself an ambulance. Basically I ended up in A&E 3 times in 5 days, before being told I was suffering from severe anxiety and panic attacks.
I was shocked, as was everyone that knew me, and I went through the whole 'feeling alone - no-one knows how I feel' thing. The emotions you feel are incredible (and very scary).
I have been having therapy and taking medication since then, and also doing a lot of research. It has given me great comfort to see how common this is, and that you can get through it (or at least learn to live with it).
I just take each day on it's own merit at the moment, and try to feel pleased with what I am achieving rather than frustrated with what I can't.