Well, it depends on what was seen. Sometimes u/s dating differing from lmp dating can be an issue, but if you are very irregular with your periods, that can explain the discrepancy. Was a heartbeat found?
Differing dates would not indicate brain damage or anything being wrong with the baby though, so don't worry about that. And egg white mucus is very normal and common around ovulation time.
I wouldnt worry to much, im due my ultrasound on 13th and my last day of menstrual was 19th Nov so I should be 11+4 now. I also had thick mucus discharge. This could have actually been at the time the egg was inplanting. I wouldnt worry at all as all are normal signs of pregnancy, in your case it was probably ur bodies way of showing u was ovulating and that.was the.time u got caught pregnant. I think im in the exact same position.