Is the baby growing in my boobs?!?!

I can't be the only momma with this problem. I've always been heavy chested (34D) but this past weekend I finally broke down and bought some new bras. 34DDD & 34G! And I know once the baby arrives they're going to get even bigger. Since I suffer from tender breast, as soon as I get home from work all I want to do is rip my bra off my body but I fear they'll become super saggy. So am I safe to let loose from around 6pm till the next day? Or should I keep a bar on until shut eye?