Dead Space 2 issues...

I'm playing the CE edition for Xbox 360 I'm at the point where TE necromorph is chasing me and my game keeps bugging out wont reload I loose all my weapons I've put multiple hr in trying to fix and now I'm at the end of the game and can't finish I need help so I can move on to dead space 3 please I just want to finish the game I payed 100 bucks and this is not right to sell me a broken game!!!