Gaining Weight

I'm 5'0 and my resting weight is 98lbs. I am trying to gain weight. Eating more meals, snacking, protien shakes, etc. It helps me to maintain my weight more, but I still can't gain anything. Goal is 103 which is what I weighed as a Freshman in college. Was a athlete, worked out twice a day and ate three full course meals a day sometimes four, but as I am no longer in school it is hard to workout and eat as I did. Any advice? The struggle is real...