What Causes Vaginal Pain During Pregnancy?

Hi, I am currently about 6 weeks pregnant with my fourth child. During my last pregnancy, at about six months in, I started experiencing a very painful stabbing sensation in the upper area of my outer labia. From the top of my clitoris spread outward toward the lips of my vagina would have a sharp, insistent, stabbing pain that could last from minutes to hours. This would usually occur while I was lying down, but sometimes sitting as well.

It worsened throughout my pregnancy, and by the time I gave birth, I could barely sleep at night due to the pain. It was constant. I asked my obgyn at the time,and he had no idea what I was talking about, and I was a little embarrassed to ask more about it. After I gave birth, the pain went away and I haven't thought about it since, until recently.

In the past month or so, the pain has started to return. It is not nearly as bad as when i was pregnant before, but I am terrified that the pain will get to the levels that it was before I gave birth last time, and I think I will probably go insane before I can deal with those levels of pain for nine months, it was excruciating.

I need help figuring out what is causing this intense pain, and if there's a way I can alleviate it even a little, it is so painful, and even thinking of having to go through it again is making me sick to my stomach. Help!