I have got a very tight chest and pain on breathing, went to a&e last night who told me it wasn't heart problems any ideas what it may be?

Anxiety: Stress, panic, exhaustion. You are holding your stress in your chest so tightly it is causing the muscles there to fatigue and your body is screaming at you to fix this. You need to find a way to manage your anxiety in healthier ways. You do not need the er. This not your heart.

Yes: Muscular strain and pain (the intercostal muscles of your chest wall) can cause your exact symptoms. I assume you have no fever which might reflect pleurisy or pneumonia. Try taking your Ibuprofen or naprosyn, (naproxen) but relaxation techniques may be of even more benefit. Check out: http://dawnbuse.Com/relaxation.Htm.