I just got my medium cups today because the small cups were too small (all my breast tissue did not fit in them, though I did not have trouble with the suction/seal with them). I decided to exchange the smalls and got mediums which arrived today. However, I am having a lot of trouble trying to get it to seal and stay on. I just spent over 30 min trying (lying down, sitting up, etc.. and also tried placing them in different positions on my chest) and it will not suction. My forearms are sore from all the pumping. I used plenty of lube (tried oil and then cream, and smeared it on the edge of the cups too). The cups fit me across the chest with space in between but I guess because it is hard for the cups to lie flat, so I am unable to get them to stay sealed. I got it to work only once but when I sat up, they unsealed. Also, if I press them against my chest hard, I can start to begin to get the vacuum but if I loosen my grip, the "fart" sounds come out and they unseal. It is very frustrating so I gave up. Any advice? I am so disappointed. 
Do the contoured cups work better? Does it mean they are contoured so they fit around your chest better?
Do the contoured cups work better? Does it mean they are contoured so they fit around your chest better?