I'm not a doctor, so I can't make medical assessments, but I do have herpes and can relate to you.
I was in the same situation when I first found out I had herpes. Several times I had little tiny bumps on my upper butt area that itched like hell and eventually would scab over. I thought it was an allergic reaction or some kind of skin rash. I went to the doctor and she took one look and told me it was herpes. The blood test confirmed.
I still get outbreaks in that area and it seems weird because it's not the textbook idea of a herpes outbreak. It's on the fatty, fleshy part of my butt, several inches from my anus, creeping towards my lower back. I'm assuming it's more in this area that you're having the blisters, instead of directly on your genitals.
You can get outbreaks here because the herpes virus actually lives in your spinal fluid and comes to the surface of your skin through the base of the spinal cord. That means that anywhere in the genital/buttocks area you can have an outbreak, regardless of what type of sex you're having.
I wish I could give you a better explanation, but the truth is genital herpes can manifest itself in many different ways, the aforementioned being one of them. So I find it's important to keep an open mind about how herpes outbreaks appear and act, instead of thinking there are the same symptoms for everyone all the time. It's too complicated to generalize.
For more information you may want to check out our Symptoms page as well as the Just Diagnosed and Treatment pages.