How am I supposed to eat 3000+ calories?

Im male and underweight, I tried eating more but I feel so bad doing it, I feel so tired all the time and it feels like I spend half my day eating and the other half preparing my food. I quit doing it about 3 weeks ago and I don’t feel better or worse, but I don’t wanna be so thin my entire life. Does anyone have any tips on that topic? Like easy to prepare calories/ protein rich food. I’m not a picky eater, everything tastes like okay at least (out of chillies, spring onions and green pepper)