I am glad you are seeing a doctor. Having chronic diarrhea that causes weight loss is a concern that needs medical attention.
I had weight loss issues following my hysterectomy from lack of appetite. I have also had weight loss issues from gastro issues and when trying to find a balanced diet to level out my sugar. Since I am naturally thin, I can't afford to lose even a pound or two and when it becomes 10 I am in trouble. At various times, I have worked with different Dieticians and a Nutritionist so I can share some tips they gave me.
One, it can be easier to consume liquid calories. Following my hysterectomy, I was ordered to drink two High Protein Boosts per day. One Dietician had me add powered milk to anything I could such as mashed potatoes, Carnation Breakfast, milk, shakes, etc. That added calories and nutrition without me having to really eat more.
Puddings, yogurt, and jello can be easier to eat as well and can easily add fruit, nuts, granola, cereal, etc.
You should also be keeping a food diary. This could help you see if a particular food is causing the diarrhea or no. I have IBS at during my worst time with it I could not eat lettuce, cabbage, vinegar, ice cream, a fast food meal of hamburger, fries and a soda because high fat nailed me, or a whole list of other things. If I had those foods, I was racing for a bathroom within 15-20 minutes.
I also cannot over eat. If I do, it induces cramps and diarrhea. So, I try to eat smaller, more frequent meals.
Try not to panic but do get medical care. You also need to make sure you are drinking plenty of water as running to the bathroom can be dehydrating. Eat what you can and don't focus so much on "healthy" foods at the moment. No, don't start eating lard or Mayo by the jar! But if something sounds good, eat it even if it is not carrots and lean meat.
in there and keep us posted!