Confused from my GI

I have been having all kinds of stomach issues, diarrhea 5+ times a day, debilitating stomach pains, blood in my stool, weight loss. I have low IGA so the blood work showed nothing. The GI did an endoscopy and colonoscopy and said everything looked normal aside from an excess in stomach acid (which he said could be from the prep). Well they called this week after receiving the biopsy and said they saw inflammation in my colon and want to treat me for colitis. And I’m lactose intolerant. I have a course of deltasone and then they want me to start mesalamine and budesonide after that.

My boss is kinda a loon, so I asked for documentation from the dr so I could show my boss that I’m not intentionally skipping work. The dr was real weird about and said “well we don’t have a diagnosis but I’ll send a letter that says you are under my care and to excuse you”.

My question is: what more do they need for a diagnosis and what does this all mean? It has been a lot for me getting this news, so I didn’t ask at the time when he called me. I’m kicking myself.

Appreciate any help!