How did you know you were ovulating at the time you had sex (and I'm going to assuming this was unprotected intercourse).
If it was, and this took place on March 12th it would be too soon to show a positive pregnancy test since it's only March 13th. In other words, conception occurs in the fallopian tubes and until the fertilized egg travels down to the uterus and implants, the body is unaware of this pregnancy. This implantation takes several days to occur after conception.
Frankly, spotting isn't all that unusual if one has sex soon after they complete a menstrual period. This may be what is happening IF the intercourse happened right after you completed your period.
If you remain concerned, wait a week or so and take a home pregnancy test. They are quite accurate.
One tube will not destroy the other. Eggs are typically released in different sides every other month; one month on the left, one month on the right. If one of the tubes was to be surgically removed (and this may happen if the pain continues) the other tube "takes over" often and eggs would be released to that side each month.
Many women with only one fallopian tube go on to have perfectly normal pregnancies.