What Causes Upper Abdominal Discomfort And Pain Post Antibiotic Treatment?

I had gum surgery last week,Dec27,& took 4 X150 mg Clindamycin before& 1same later that night&, if I remember correctly, took 1 same, next day& then had uneasy stomach: I called my periodontist& he said to stop it. He originally prescribed it because in1988 I had bacterial endocarditis ( I have mitral valve prolapse) associated with a stroke. Friday I was cooking and ate a large quantity of vegetables, including raw broccoli( without peeling off outer part, and cooked sweet potato skins, and sautéed onion& sautéed& raw celery. Friday night I had Intense stomach pain-mainly in upper abdomen- where ribs come together under breastbone. I saw a doctor-friend& he advised me against going to hospital (in 2013 I had an operation on emergency basis for strangulated hernia( during time I was taking outpatient chemotherapy for nonHodgkins lymphoma)-followed by similar surgery the following year to open blockage caused by scar tissue. I did feel much better Saturday& have Ben eating some. Today I still have some feeling of a chinless in same stomach area. In addition to that I m noticing that sometimes my urine s darker than my usual: please advise me Thank you very much, Judy Stieglitz YYYY@YYYY