23 weeks and ate a donut

I'm feeling really bad for eating s donut. i feel like it's gonna make me fat. i'm 23 weeks and i should be giving my baby good food, not a donut. is anyone else feeling this way or is it okay to do that sometimes. I've struggled with an eating disorder my whole life and now that i'm pregnant it's become really really hard. I don't know what gonna make me gain excess weight and what's not.