Healthy foods with lots of calories that won't make me feel sluggish?

Protein won't make you feel sluggish. You can eat eggs fried in er, bacon, well marbled steaks, ham, fried chicken, crab dipped in er, cheese burger without the bun (or with if you feel okay with it), all kinds of cheeses, tuna salad with mayonnaise, etc. Be sure to eat at least three times a day, and have snacks in between if you can manage it.