The pH of the vagina changes in pregnancy and these changes can cause local irritation. Sometimes, intercourse will help, due to the low pH of the semen. Cold compresses may also be soothing. You could also coat your finger with yogurt and smooth some over the inflamed tissues. I'm assuming that all other infections have been ruled out.
Yeast is the most prevalent infection, which causes vaginal itching.
These are very easy to catch and not always sexually transmitted. Use of hydrocortisone can contribute to the itching if it contributes to skin breakdown, so I would discontinue its use. There are creams which contain local anesthetics that may help. Lidocaine gel is helpful because it is a pure anesthetic. Monistat is a good choice as it would relieve the itching and control yeast.