Thanks for your question and concern. It is possible for herpes virus to stay dormant for years in human body, without making a visible outbreak. Outbreaks can be seen once favorable situations come. Once favorable situations come, outbreaks can occur in the form of cold sores, fever blisters or flare ups. Blood tests are not reliable if one with infection has not had any outbreaks till date. With outbreaks like cold sores, we can confirm the presence of virus. If your boyfriend used to have unprotected sex with his ex-girlfriend for years, there is a good chance that he might have got infected and thereby, you also can get affected. But test results may show negative, if there are no visible sores or blisters are seen. There is a chance of not getting affected, if his ex-girlfriend has got the infection recently and you boyfriend hasn’t had sex with her after that. The only way to prevent infection is to have only protected sex with partners. Also, consider testing for herpes frequently, for a year or two, if you are not getting any visible outbreak. However, there are no medications found till now, to treat genital herpes of any type. But cold sores and herpes are treated symptomatically. Hope your query is answered well. Take care.