Normally I just wear a sports bra, but for special occasions I steal one of my sisters non-sports-bra bras but I can't get the straps to stay on my shoulders, they always slip down, it's annoying, I've tried adjusting their length but that doesn't do anything, why do they do this and how can I make it stop?
Well you could try finding a bra with wider straps. I don't know how your posture is but that has alot to do with it too.
I've got a couple bras that tend to slip down. I just adjust them to be tighter than they actually need to be.
My bras do that sometimes too. Try double stick tape. I know it sounds stupid, but at the very top of the strap just put some where it hits your shoulder. If all else fails? Screw it and wear a sports bra. My other suggestion, though you'll hate it, go to Victoria Secret and buy a bra that actually fits you. It sounds like the one your sister wears isn't your size. And by the way, it's much more fun to undress someone in a real bra rather than a sports bra. Just a personal opinion...
My sisters bra's fit me better than they fit her, it's brutal... Also, I only wear them 3ish times a year, when I have to so I don't want to go and spend money which I need for other things on something I rarely ever use... Thanks for the suggestions!
They make a plastic thing that will attach your bra straps in the back, and helps keep the straps up. My posture is horrible, and my bra straps rarely stayed on my shoulders before I got that connector thing! They sell them at most local stores and wal-mart I think.