I hate myself for being sick all the time

I have a part time job. They only schedule once a week, but I struggle to make some shifts because I get sick so easily. Working in the food industry also makes me feel guilty that I might get other people sick. Having celiac and potentially getting "glutening" episodes makes things even worse! I feel so useless. If I can't work one day a week, I bet the managers see me as lazy. The ONLY reason I'm going to the dr's today is because I fear that if I don't, my dad will think I'm lying. But I'm scared I'm gonna lose my job