I've been eating badly these last two weeks
Why have you been eating badly?  Were you sick?
I saw a show and they were talking about bad relationships, I started eating greasy food to piss my girlfriend off.
You should not hurt yourself to try to annoy someone else. It is spiteful, and frankly pretty obnoxious to behave that way, since you are the one who will be hurt.
It's not like I'm putting poison in my food. I didn't do it on purpose to actually harm myself.
Well, that's good that your decision to eat badly was only temporary.  But I have to advise against actively trying to annoy your girlfriend.  I don't know if you're doing so just for fun, or if there is a deeper issue, but you don't want to upset her like that.