How far to push it??

Hi There - Really would appreciate some thoughts on this!

I am hugely overweight but I have been exercising and trying to mix it up with treadmill/weights/bike/swimming/etc. I have been doing this now for almost a month several days a week ---

I know that with the aches and pains one pushes through and it does get better (different things hurt - so it works)

However - it has become really quite humid and when I was trying to do the interval training for the second time today where you push yourself to the limit for two minutes and then walk slowly for 1 minute and then push intensely hard for 2 minutes and back to walking yada yada - I got tight pinching in my chest on the the left side. this was when my heart rate was at 90% of the max heart rate. It was in the 6th time of the high intensity burst not the first 5 times.

I brought my speed on the treadmill back down so that my heart rate was back in the 70% and waited longer than the minute rest and in fact waited 2 minutes and then pushed again up to the 90% and before the 2 minutes were over I had that pain/pinching so I finshed the 2 minutes at more like 85% but it was uncomfortable. I then waited 3 mnutes before going back up to the 90% and again the pinching came back - this time along with a side ache and an uncomfortable all over feeling. I did my last "burst" at more like 80% and did not do my final 10th burst --- I did walk on the treadmill for 15 minutes in the 75 - 80% to try and make up for the lost 2 miuntes.

Sorry to make this long - but what I want to know is should I ignore the pinching/uncomfortable feeling and push through like we do with other muscles in the body .... or should I modify what I am doing? Could this be because of the humidity?

Hugs - Dia