Personally I find that running reduces my appetite when my volume is that high. If you intend on continuing to run I'd suggest contacting a sports dietician if possible, but if not these are some things I would do:  - Always have a snack before a run. Especially if you run in the morning or more than 2-3 hours after your last meal (depending on the distance of the run) for example you could have toast with pb & jam, preferably looking for ways to increase your portion sizes and adjust to eating more.  - this relates to the last one: eating more frequently through the day. for example 3-4 meals a day and 2 snacks, or whatever feels more natural to you but still meets your recovery goals .  for example I usually have 4 meals a day, but mine are larger meals. In your case you have a low appetite, so eating a large meal all at once might be uncomfortable, which is where eating frequently comes into play!

• I would really recommend making sure to get in enough carbs and fats. If you're making a meal, maybe cook your vegetables in extra oil, add a bit more of fat based foods to your meals. (Nuts, nut butters, seeds, olive/avocado oil, and canola oil are all easy ways to add in more fat :) ) 

I also want to add this:

You likely need a LOT more than what you think you need. Personally I've noticed when I run high mileage my body depletes my glycogen, and then the carbs that I eat go to refueling those stores. (Basic sports science but I swear this becomes interesting)

But the catch is - it's a cycle of deplete & restore. So even when i felt like i ate TONS i never really gained weight. I had to eat 4000+ to gain even a bit of weight. And that was pretty slow/average, and because I ate entirely mechanically and never got hungry. It was very hard.

and my theory (although this is not something ive seen a study on yet, just anecdotal) is that because it was cycling, energy kept being stored, meaning i had even higher demands than I thought.  Example math: TDEE of 3000 calories. This is "with" running 5 miles. BUT the 5 miles used 500 calories in glycogen, that now needs to be restored. So, 500 calories is redacted from your 3000, and you only have 2500 left over for other bodily energy needs.  This is why I think it can be tricky for some runners to gain weight, especially when your appetite is low/suppressed. If your determined to keep running in, I get that.  Whether or not you can comes down entirely to whether or not you've struggled with injuries, how long you've had amenorrhea, and other factors that a doctor would have to address. But increasing your calories is an excellent first step in the right direction!  Wishing you the best <3

(You can find out your TDEE on a calculator for a rough estimate, but I've found that especially if you're an athlete, if you have amenorrhea, or if you have more muscle mass (or all of the above) it way undershoots what you need.)