Exactly 1 Month Ago I Had A Lot Of Abdomen

Exactly 1 month ago I had a lot of abdomen pain coupled with a low grade temp in the evenings and a very swollen abdomen. Not sure of the cause, Urinalysis came back normal and Ultrasound had normal results. Since then, my abdomen pain and swelling went away the following week but I have continued to run a low grade fever in the evening. I usually run around 97.6 F and have had fever of about 99.4-99.8 F. The only other symptom is I do seem to be a bit fuzzy headed and I get a few headaches every now and then but otherwise I feel normal. Any idea what might be causing this?