I know this is for the skin, but...
en.wikipedia.org/wiki/Cutaneous_condition#Primary_lesionsIt seems like from that an erosion is the same thing as an ulcer, but not as bad.
You haven't been on NSAIDs recently, have you? Bit of an obvious question, but they can cause ulcers in the small bowel.
If the villi were normal, I'm guessing that rules out possible Coeliac Disease...
I think you need to keep pressing for answers. I would still seek a second opinion, even if your biopsy shows up as normal. It is possible for healthy folks to have erosions in their small bowel, but the key word there is 'healthy': you are not healthy at the moment. I wouldn't be at all surprised if you had early stage Crohn's, but my thoughts are literally meaningless I'm afraid: I cannot provide the diagnosis.
Good luck with finding an answer soon :-/