Ugh. Help

So according to my menstrual cycle and my babies fundal measurements and US I'm due the 17th of October, but because in the beginning he was so small they have my due date at 31st of October and even though since my anatomy scan I've measured two weeks ahead they won't change my date! I mean even at "14 weeks" you could see he was a boy which normally would be too soon to tell but even then he was measuring 15 weeks and 8 days. Now I'm supposedly 32 weeks measuring 34 and beginning to experience vomiting contractions the whole 9. This is also not my first pregnancy, it's my third. I'm just worried if I go into labor at what they have as 36 weeks they might try to stop me. Has anyone dealt with this? Measuring ahead and all that.