What Causes Frequent Breaking Of Rib?

Hi, this is kind of embarrassing, but I broke my upper right (2nd?) rib last night whilst having sex. It's the 4th time I've fractured the same rib in the past 8 years - I'm just wondering if I should get checked out to find out why the same one keeps breaking? I'm an otherwise healthy 29 year old woman. I've broken the rib in the past simply by being hugged, falling and bumping it and coughing too hard! When I did it last night I wasn't being particularly active with my partner, his hand was on my ribcage but he wasn't pushing hard. I'm just slightly concerned that it keeps happening - surely I'm too young to have brittle bones?