Hey guys.
I have a bigger chest and when I weight traine or do cardo I feel like my binder is way too constricting... makes it harder to breathe. But I'm really not comfortable with my chest. What do you guys wear when you work out? Any tips for me?

I am large chested and I bind all the time - even working out.  I can't not bind.  I do wear an underarmour shirt under my binder and it feels tons better.  It doesn't cut into me as much

This may not be what you want to hear, but I don't bind when I need to be able to get as much air in and out of my lungs as possible.  Psychologically speaking, I'm an athlete first and looks-conscious second.  I wear a good "masher" sports bra (like the Frog Bra from Title 9 Sports) as long as it lets my ribcage expand fully.  That's a must for both lifting and cardio.  Of course, I have been blessed with AA's, so my experience is very different from yours - what I look at in the mirror and groan at as "too obvious" would probably be your dream chest.  :-/ 

I have tons of issues with not binding too. I usually wear two binders to be as flat as I can, but when I start working out again I'll have to cut down to one. I found a really comfortable one from Love Boat, the high performance velcro binder, which is so comfortable I hardly even notice it's on. It's got decent results too, but it's still unnerving leaving the house wearing only 1 binder.