I desperately want to gain weight.?

I'm 18 years old. Asian. About 5'1. 98 lbs(now). I used to be 103-104. That was the highest I could ever break. I ate a lot of junk food, soda blahblah. I started losing weight 2 months ago when my bf and I broke up. Now apparently I look unhealthy looking. I'm just sick of people telling me I look too skinny and I used to look better. I eat now, but its not as much as before. Whenever I eat my stomach starts to hurt, like i ate too much, even if it's such a small amount. I know, i shouldn't be losing weight over some , but it happens. So what is a good way to gain weight and put some healthy meat back on my body? I also stopped eating fast food and stopped drinking soda completely when we broke up, so maybe that was a reason why i started losing some weight..since that was basically all i ate before..i don't know. i just want to gain weight in a healthy way. i don't want to go back to eating fast food and drinking soda..im actually drinking a pepsi right now and it..is..grossssss. please help a meatless girl out. please don't say something like "love your body" "who cares what people think" i just don't want to end up like nicole richie.