70 hours a week in itself is stressful, when you feel yourself getting panicky, breath in real deep through your nose hold it for 3-5 seconds then breath out through your mouth, do it 3 or 4 times, it will calm you down. Also, you're probably holding yourself tense which will cause the chest muscles to hurt. Try to relax, I know it's easier said than done, but you've been thru this before and came out OK, you will again this time!