it does sound like you could be having a panic attack. you should go to the doctor though. any time you feel like you might need to go to the doctor, do not hesitate to go. sometimes you can be really sick and not know it. i put off going to the doctor for months and months and felt worse and worse to the point where i could barely move and when i finally went i found out i only have a pint of blood in my body! very low. i had to have four blood transfusions. all because i sat at my house reading symptoms books and convincing myself that it was all in my head. the best thing you can do is go to the doctor. it's okay to go to the ER for a panic attack, too. my boyfriend had an anxiety disorder and went to the ER numerous times.
Hi. The feeling of impending doom and not breathing properly sounds like symptoms of a panic attack. I agree with jmom3, go to a doctor. You should have your thyroid checked because a thyroid problem can cause those same kinds of symptoms. Your doctor can order a metabolic panel, thyroid check which can be done with a simple blood test. Or go to the ER next time and tell them about your symptoms. They can do the blood work there as well.
Do not hesitate go to the Doctor and they can examine you and run tests!