That happened to my best friend when she went on yasmin. She went from a c to a full d and she said it was horrible. She too now has stretch marks and she had to get off of it because it was doing horrible things to her body.
I am a b and I am on ortho lo, my boobs are still about the same size, maybe a little fuller but I fit just fine into my bras. Thats fine by me being so petit and all I was actually really worried that would happen to me too but thank god im still normal size.
I havnt really had any side effects on ortho lo, so I think it's a keeper.
If you experience a lot of weird side effects you might want to look into pills like ortho lo and the "mini pill"...Good luck!