Welcome to our Forum. Please be patient. The MedHelp statard is that questions should be answered within 24 hours of submission we do far better than that but the site is not manned 24/7. I will be pleased to comment and provide some suggestions.
Your problem is a difficult one and I suspect you will need further evaluation, probably by a dermatologist. I completely understand why having recurrent "cut" close to your rectum would make you worry that this could be herpes however it is certainly not clear that this is what is going on. The fact that you have the recurrences so frequently is more often than is typical for herpes- on average, HSV recurs about 3-4 times per year, not monthly. Further, although they rarely are negative in persons with infection, your negative blood tests is strong evidence that this problem, whatever it is, is not herpes either. I have several suggestions which may help you to sort this out:
1. You need to have a PCR test taken with a swab from the recurring "cut" the next time it recurs. The sooner after it appears, the more likely it is to be positive IF it is herpes (which seems unlikely). These tests are highly sensitive and if this is herpes and you get the test soon after the sore appears, it should be positive if this is herpes.
2. Second, I would suggest that you see a dermatologist about this problem, again, preferably if it can be arranged at a time when the lesion has recurred. There are other dermatological problems that can recur in this way.
I hope these comments are helpful. Please let us know what the dermatologist says and what the PCR test shows. EWH