If there really were blisters, and if a health care provider thought herpes was sufficiently likely that s/he prescribed acyclovir, you can be pretty certain you have genital herpes. Chafing alone, even from very frequent and vigorous sex, rarely causes such problems, especially in men. And both the swelling in the groin and your run-down feeling are typical of herpes, but not of chafing or vigorous sex.
So I'm betting this is indeed a primary case of genital herpes. Follow your provider's advice about treatment and follow-up. And if not yet done, your partner needs to be examined and tested for the infection, even if she says she is 'sure' she doesn't have it.
In the meantime, you should start reading about genital herpes. Beware of websites that are not professionally run. Start with the information available from my former health department (www.metrokc.gov/health/apu/std), the American Social Health Association (www.ashastd.org), CDC (www.cdc.gov/std), and/or the Westover Heights Clinic (www.westoverheights.com).
Good luck-- HHH, MD
One more thing: Make sure your provider does a test to determine the virus type infecting you, i.e. HSV-1 or HSV-2. That will make a lot of difference in predicting how frequently you might have recurrent outbreaks in the future and the risk of transmission to future partners.