When did I concieve 2nd pregnancy?

Ok my periods are irregular so I rely on OPK's and my last period was 10/10 ok I OV on 10/22 and BD on 10/20 and 10/21 PG test positive on 11/1 line was so faint I could not believe it so I went to the free clinic 11/3 and it was indeed positive but they put my due date at 7/8/11 I have an appt at the OB but that is way in december can any one help?