I had intercourse 5 days before I had a POSITIVE pregnancy test, is this the possible day I conceived?

Tough to. Believe the events from five days prior led to positive test. It's possible. But I wouldn't bank on this day of conception.
Not likely. Conception, as defined by the generation of a fertilized ovum, occurs within day or so of the sex. However, it takes about two weeks for the embryo to make enough HCG to produce a positive pregnancy test. If you had sex earlier, about 10-14 days before the positive test, that is likely to be the relevant episode.