Shortness of breath when I walk

I am diabetic and had an MI in 2000(India).The doctors put a stent.I have LAD.The doctors told me that I had another artery getting towards 70% blockage.I am on aspirin and diabetes medicines.I stopped taking statins regularly as they were a pain in my leg muscles.Every year, I take a maximal stress test to check my heart condition.
Since last week, suddenly I am having shortness of breath when I walk even for a short distance..like less than a block.When I take the nitro pill,I am ok. Now I am afraid to take the stress test...Do you think its my other artery (70%) ready for a stent?What are my options to consider before I visit my doctor today ?I am 40 and haven't been exercising regularly.But I am a vegetarian and try to control my diet.Could just medication work for me or will I have to go the catheter way?
Thanks in advance.

[rubyhall]

Hello all,
I am back from the hospital visit with three new stents in the RCA.(which is new to me).
Old stent is ok and the 70% is now 85%.The doctor did not even stress-test me.
Hence,if you are a heart patient and suffering from shortness of breath even while walking,just go to the doctor.You'll save your self. :)