Hey guys, im 25, 5'8, 145 lbs.

I've been in and out of the gym for the past 5 years or so. When I was 17 I got my body weight up to 160. Due to personal reasons I stopped working out and lost down to 129. I've been eating better for the past 8 months or so and working out at least 4 days a week. I know i'm not eating enough, but im wanting to bulk up, so I would like some advice on how to improve my diet. Also, I have a hard time eating an insane amount of food, as I just don't have the appetite for it. I can work my way up to it, but I would like to try to work myself into eating a large daily amount of food. Is there any diets that would work like that? Any info or advice is appreciated