This is a TL;DR list I wrote to help when my cousin was struggling to eat and having stomach aches whenever he did eat:
By medical definition, “anorexia” just means low/no appetite. Anorexia nervosa is the intentional eating disorder.
Anorexia can cause stomach pains, especially following a meal. Fix this by eating frequent small meals or snacks.
Cut your diet down to bland food and introduce different things in slowly or document your food intake to figure out if there are any allergies/intolerances causing you to not feel well.
Make food a routine using external motivation to eat, such as alarms, calendar invites, or planning meals with coworkers/friends.
Suggested rule of threes: 3 meals, 3 snacks, at least 3 hours apart. Set a timer!
Find easy meals you can always eat. Whether it’s takeout or just something super easy to make, have a staple you can always fall back on when you don’t want to think about food. A rice cooker with a steamer basket was a game changer for me, and lately it’s been Trader Joe’s frozen foods.
Learning #1 was what made me realize my relationship with food was unhealthy and needed to change. #2-3 might not apply to your situation but I’m leaving them in case anyone else needs it.
#4 and 6 really are the answer to your question. When I got my first job out of college, I ate lunch daily with coworkers even if I had no desire to eat, which greatly helped the last thing I’ll share: I redefined what I thought of as hunger.
I realized even when I didn’t consciously feel the need to eat, my body had symptoms. I paid attention to things like lightheadedness, a tightness in my stomach, and shakiness, and started considering those to be “feeling hungry.” After forcing myself to eat more consistently and listening to my body, I actually started to feel hungry on a regular (daily-ish) basis.
Oh, and for a year or two I lifted weights 3x/week and that made me hungrier than I’d ever been in my life. The first three months I always felt hungry. But that’s a bigger commitment than the other suggestions :)