so i'm an abnormally thin(concave chest ftl) college track athlete, i'm 6'0 and 140. i tore my quad last year and took the season off and have lost more than 10 pounds since then. ever since, i found that i've lost a lot of my appetite and i've stopped doing all the sport-related lifting since then(mainly squats, cleans, snatches). we had some upper body in the daily routines but not enough as i'd like. anyways, i'd like to be up to at least 155 by the time i start training again in about 2 months. doable? i've never lifted to gain muscle mass/weight, i've never been on any sort of diet/supplement, i've never been to a gym besides the ones at my high school and university, and i've never had a personal trainer. i'd like to work on my arms, core/abs, and pecs(especially inner), mainly just upper body in general. any thoughts/suggestions/advice? it'd be greatly appreciated!