You may bring a motion in the court asking for contact with your girlfriend, but this should be your last resort. You should try working this out with your probation officer first, as not having contact with a woman who is pregnant with your child is somewhat unrealistic. If your probation agent continues to be unreasonable, you could try speaking with your probation agent's supervisor. If that does not work, you may want to start considering the motion before the court.
Just keep in mind that going over your probation officer's head will likely not endear you to him or her. And your probation officer may decide to terminate your probation early if you fulfill all the conditions and serve at least half the term.