If sexually active (serial monogamous), how often should i have hiv test?

Depends: If you enter a new relationship it is wise to have your partner tested, having the male partner using condoms until cleared. Then, depending upon your confidence in your other partner, either continue using protection or if you are willing to take the risk of a potentially fatal disease, test yourself about every 3-4 months. This is a very difficult issue since many people are not open about sex.