I Am Only Taking Short Gasps Of Air Which Leaves Me Lightheaded And Nauseous

For a while now ive been having problems with my heart. In the beginning, it was just an irregular heart rate and sharp pains when moving too quickly, i was prescribed atenalol, and then propranolol to help calm it. But recently, (the past month or so), the pain has been getting worse, as well as my heart rate soaring even when I am resting. When this happens, my breathing quickens but im only taking short gasps of air which leaves me lightheaded and nauseous. This used to last about 10 minutes or so, but within the past week it has been going on for more than hour, which has caused me to black-out on several occasions. My boyfriend is constantly worried and demands i go to a e, but ive been relying on the medication, (which hasnt been alot of help) and am a little worried about having to go to hospital. What im asking is, what is causing the chest pains and breathlessness , and should I go to a e ?