Yeah it shouldn’t be too tight, My surgeon told me that it’s not good for your sports bra/macom to be tight. You need to be supported but not restricted…. although i don’t really know how much any of this stuff effects you in the long run, everyone says something different! xx
Unless the D cup bra is extremely loose then i doubt it won’t be providing the support necessary and since you say the C cup bra is too tight, the D cup should fit better. You don’t want a bra that’s going to be digging in as that is defs too tight and will probably be uncomfortable. xx