Braxton Hicks

When would it be time to call your Dr? I am 25 weeks and I was having them 30min apart. I work 8 hour shifts and am on my feel all day,5 days a week. Yesterday I didn't get a break to sit or drink water for 4 hours and I noticed them being more frequent that evening. Figured it was due to dehydration. My son was preterm and I might be over reacting cause I am worried about going though that again. I might just send a quick Email to my Dr office but didn't want to if they subside through today.