Valtrex without a positive swab test to confirm a herpes infection is an inappropriate treatment for a sore throat. That is especially true given you were not yet sexually active.
With that many partners, I think testing for HSV of one type or the other is likely but not 100% certain. You could start with an IgG test or if you want the best test, the herpes western blot from the University of Washington will give you the most accurate results. I do think you should find out, even though you are slowing down a bit. You could be more religious about condoms if you were positive and possibly take daily antiviral medication to reduce the risk even more of infecting partners.