so I would stick with Majikat's recommendations of having sex
from cycle day 12 to cycle day 19 just to make sure you cover your ovulation period
, however bear in mind that you will be releasing an egg closer to day 16 than day 14.
your weight should have no effect on the semen leaking out of you..it's fairly normal, and during certain parts of a woman's cycle her cervix will be most closed which will in turn push more semen back out of the vagina instead of up into the uterus. However...