I am feeling sick, what could I have?

I have *nausea *sometimes diarrhea only if i eat hot foods (never happened to me before) *stomach aches *loss of appetite *i do not eat unless i am really really hungry (cause of my stomach aches) *i never vomit *after i do eat a burp a lot. *I maybe only eat twice a day, or once, and a few nibbles on food *do not drink very much fluids cause im not thirsty. i'm 14 and my mom says i have to change my diet or im just growing, but I think it could be something else cause i eat a lot of healthy foods otherwise. I used to always eat big meals but i cant anymore and this started pretty much the exact beginning of summer and lasted til now, which means i am not having the greatest summer.:( also idk if this has to do with it but i had staph last year and have asthma/allergies> which i had to go to the hospital for. please help meee thank you guys please no mean answers