I Have Noticed Recently I May Be Losing Weight Without

I have noticed recently I may be losing weight without trying to. I work a pretty stressful job and sometimes I skip lunch. I just had a dislocated patella about a month ago. I'm 35 year old man. I'm 6'3" and normally weigh around 205 lbs. I'm down to about 196 now. I've had stomach issues with diarrhea and stomach pain but it's not consistent and happens once in a while. What can be causing the weight loss and should I just eat more and stop skipping lunch?