I went up in my loft to get xmas tree down, as I was stepping on the beams I noticed one went down as I stepped on it, have got loads of cracks in my bedroom ceiling below. I'm worried. I live in a rented property from a housing association. What do I do, and am I worrting for nothing?

Worst case scenario, if beam weight is too much for s/r to hold, some of s/r could fall down. Notify the association that there is a broken ceiling beam above your bedroom. They are responsible for structural framing.

Be sure to remove anything stored in attic away from that area.

Chuck