29week now had always difficulty in breathing

It is likely both hormonal (can cause your airways to have more mucous/ swollen than usual) and the uterus growing upwards, thus pressing up against your diaphragm. I see a respiratory medicine doctor for my chronic illnesses, and that was explained to me by goth my gynae and respi doctors. Unfortunately shortness of breath is a feature as pregnancy progresses. If it's of any consolation, it usually goes away postpartum. If it worsens and affects your daily activities, perhaps bring it up to your gynae at the next visit. Hang in there!