Measuring ahead

Im 21 wks 5 days, an my son has been measuring ahead each sono I've had. Im considered high risk, due to previous miscarriage which they think was due to my cervix plus i have pcos as well. But he has been measuring ahead , Dec.9th- 6 days ahead, Dec. 23rd- 3 days ahead, Jan. 6th- 6 days, Jan. 20th- nearly 2 weeks ahead, Feb. 3rd- 9 days ahead. Has anyone had there baby measure ahead an he or she come early? An ahead in weight also an end up not being big when born? My son is already over 1 lb 2 ozs.