Nursing bra sizing, help!

OK mommas, I need help with bra sizing, (sounds goofy I know). I was a 34G pre-pregnancy and am now needing a bigger size. I'm popping out of my maternity bras, and I found some nursing bras that can be a 34H/I or a 34J/K and I'm not sure which I need. I'm only a month away from my due date, and I know that once milk comes in I will swell a bit, but what do you mommas recommend? I don't want to spend unnecessary money and thankfully the company has a nice refund policy. But I'm needing new bras soon, this isn't comfortable anymore. So help, please?