How do you know if you can breast feed or not?

I am a little over 27 weeks pregnant and my boobs have grown some, but not a lot (mind you before I got pregnant I've always had small boobs, about an A cup and now a B/ small C). I'm worried that I won't be able to breat feed because I'm not making enough milk? But I'm always leaking like crazy and have been since about 18 weeks. Anyone ever been in the same boat and able to breast feed just fine?