[Jesus Christ.]

She's probably tired because she sleeps too much.
Sometimes people have random cravings, I know I do...
The pill is extremely effective if taken properly.
She still had a period though, it's very unlikely that she is pregnant if she's had her period. And periods aren't always the same.
Catching the flu isn't a sign of having a bad immune system, I have a great immune system and still caught it.
Boobs get bigger around a period, and they're forever changing size any way. They could just be growing.
Nausea is quite a dominant feeling in pregnancy, if she was having other symptoms then she'd probably feel nauseous...

I doubt she's pregnant, I think you're putting too much thought into it.