Baby underweight

Hi mummy just wandering is it normal to feel breathless always and hard to walk all the time ? because my 1st and 2nd pregnancy I was so different from now ,after 6yr and now Im pregnant with 3rd baby girl at 34week now I'm feeling so weak in 5min time I already cnnt walk need to atlis seat for awhile . And my pelvic is so painful hard for me to wake up from bed or even stand up after seating down . I need advice from u mummy's! Doctor told me it's normal 😓