You do increase your chances of getting pregnant if you have sex after your test has indicated that you are currently ovulating, but if you do not have intercourse before the test came up positive, you might have missed an important opportunity to get pregnant. Don't forget that sperm can live inside the female body for a while up to five days. That means that a sperm that already got to your fallopian tubes before you started ovulating might have the best chance to fertilize your newly released egg!
For those who are hoping to conceive the gender of your choice, timing intercourse before ovulation is actually an integral part of their gender selection method, depending on the chosen gender. It is safe to say that having intercourse before a positive ovulation tests, around the time you are expecting to ovulate, further increases your chances of getting pregnant during that cycle. And just as there are indications that too much sex can affect your chances of conceiving, too little of it can also reduce a man's sperm count, thereby reducing the odds of getting pregnant.
I'll have to say this one more time. It's probably best for your relationship and your chances of getting pregnant to have sex when both partners feel like it, plus a few times more, after you got a positive ovulation test. What do you think?