Wait.. Are you pregnant?
If you are, that's ridiculously unhealthy,
&you need to talk to your doctor about this asap.

If you aren't, .I know it's hard, but you have to start eating.
Maybe start small, &work your way up. You know?
Start off with crackers like you said, plus maybe a sandwich with some deli meat &cheese.. Then the next day a sandwich for lunch, &some low-fat mac &cheese for dinner? Just take it slow, that way it will easier for your body to adjust to eating the food it needs. You can still be thin &eat foods you like. Exercise &eat healthy- don't go on junk food binges. It's hard, but if you really want to help yourself- get motivated &just do it. I've been there. It isn't fun, &you've gotta do something before you starve yourself to nothing more than a walking skeleton.

If you are indeed pregnant and had severe nausea like I did in the 1st trimester I would suggest going to get these nausea pills for pregnant women. They work wonders and I had such an easier time once I started taking them. I'm not sure what they are called or if they are available in your area but they have a pink pregnant lady on each pill. Ask about it. And force yourself to eat !