possible preterm labor?

Britney • young mom of 1 soon to be 2. due in October ♡ boy mom 👶🎈🎈

started feeling nauseous and then began vomiting bile so after started having what feel like contractions and bad back pain that went down into my legs . been about 45 minutes now and still experiencing it. should I be worried or is this normal for 28 weeks??