My discovery stroller seems to be collapsing on one side its like it's bending in the middle - can I fix this?

Hiya, Leanne,
I am sorry to say that no, you most probably cannot. The side is probably damaged to broken, and the bending is not something you could fix at home. I recommend either trying to claim your warranty if that is applicable, or simply start to think of a new stroller, because this could even be a health hazard for your kid.