Iworked my duedate out to be the 19th of August 2012 my scan dated me the 22nd and had him on the 18th I slept with sumone on the 4th of November but I am sure I had my period the 12or 15 of November I fink I may of conceived around the 26to29 of November I fink my partner is the father but just need to be sure could the scan and me both be wrong the scan dated me 12weeks and 6days on feb 12 2012 the 2week prior conception os confusing me the lad I slept with is an ex who I have my daughter with which took him and me 3year nearly before fell pregnant iwas with my current partner for 10mths just need to be sure really hope you can help

Dating is all Best Guess I'm afraid..
If there's a problem with paternity then the ONLY way to be sure is a DNA test best done AFTER the birth.

We can not say for sure 100 percent, yes most likely, but that is not 100 percent,

Conception dates are good give or take a week, sometimes two..

While not likely, it is possible first guy could be. So a DNA test is really the only way to be 100 percent sure.
Sorry