Many STDs can be asymptomatic. It is possible for anyone who has had a previous sexual partner to be carrying an STD without knowing it. Short of having a complete array of tests, there is no way to be certain. Obtaining a sexual history from your partner is a good idea, but simply getting to know your partner will not automatically protect you from STDs. Because you are in a monogamous relationship, you do not need to practice safer sex.
Many university students are serial monogamists.
That is, they move from one monogamous relationship to another. Since they are only having sex with one partner and do not think about having sex with other partners in the future, they do not feel the need to practice safer sex. In sum, they do not see themselves as having multiple partners. Yet, as many of us know from experience, some relationships end and we move on to new ones. As a result, over an extended period of time, a person could be involved in a series of monogamous relationships.