How do I gain weight if It's hard for me?

Rdzivan98
I weigh 110 at 5'7 and I'm 18 that's really bad. I use to weigh 120 and lost 10 pounds in just 4 months. I eat a good amount of food but I feel like it's not enough. Most of the time I get full so quickly and other times I'm not hungry enough to want to eat. I feel like this is really hurting my health and I've tried to consume more meat for protein. What do I do?
How do I gain weight if It's hard for me?
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