Cure Candida

Because I had this insane crazy roommate and right when things blew up between the two of us, I began getting symptoms, digestive, etc. It turns out I have candida yeast infection. Is it possible that he put something in my food, and if so, how would it be? spitting into it? putting something else in it? please, this is weighing heavily on my mind.

May be. But why he/she will do it. If you think of your bad relation with that person, avoid them.
If it is not possible to change the room, try to make good relation with him/her. This is a very critical situation.