Having a bad day today - sat at work really anxious. Haven't been sleeping for over a week now so think that's not helping. Waking up anxious and worrying every little twinge in my chest is going to turn into a full blown heart attack.
If I hadn't slept for a week, I wouldn't just be having little twinges, I'd have so much chest pain I could barely breathe! No wonder you are feeling rough. Tiredness is one of the biggest causes. A doctor once said to me that you often get chest pain with exhaustion as it is nature's way of trying to make you rest. If it hurts to move, you are more likely to stay put!
Walking: I don't have your problem, but I did go through a phase of panicking about walking anywhere after I collapsed once when I was out. If I had to walk anywhere, I would panic it would happen again, which of course made my breathing funny, which made me light headed, which made me panic more... I built it up in tiny amounts, gradually extending how far I went & eventually it eased.
Typing - make sure you do lots of relaxing exercises regularly - shoulder shrugs, rolls etc. It's really easy for the shoulder & neck muscles to tense even if you aren't anxious. Also, check your chair, desk height, screen height etc - it's amazing what a slight difference of position can do.