Am 6 months 1/2 pregnant its my second pregnancy, and i feel breathless and weak all the time my chest feels tight and feel nauseas help me please?

Seek help!: Please seek help as your symptoms could be related to many different but concerning issues. It could be related to a low blood count, like anemia, or from significantly elevated blood pressures, or some compromise of your heart and/or lungs - like peripartum cardiomyopathy. I would not just rest on these symptoms as they could be a sign of danger to you and your unborn child. Best of luck.

Calm down.: It might be heart attack or Panic attack, go to the ER and find out what is going on. make sure to follow up on aftercare with psychologist/psychiatrist for meds. And a cardiologist/exercise for heart/stoke issues.