Any time you develop new symptoms such as itching in your pubic area, especially shortly after having sex, you should have it checked out by a doctor
. There are not that many STDs that cause itching in the pubic hair as their principle symptom. Probably the only one worth mentioning is pediculosis pubis (also known as pubic lice, or "crabs"). Common STDs such as gonorrhea, chlamydia, and herpes would probably not cause itching in this area as their main symptom.
Keep in mind that there are many other things that cause pubic area itching other than STDs. For example, probably the most common cause of itching in that area is a skin fungal infection called tinea cruris (also known as jock itch). If this is what you have, then a simple topical anti-fungal cream is all you need.
I suggest that you schedule an appointment with your primary care physician
. He or she can listen to a description of your symptoms and perform a thorough physical exam. If your doctor finds something that he or she thinks needs treatment, then you can get a prescription right there. If nothing is found on exam, your doctor may send off tests for the common types of STDs to make sure nothing is going unnoticed.