Is there room for a King Sized bed in your room?
Perhaps a king size memory foam topper 2 or 3 inches can be put on a floor someplace and this would do for a bit.
Essentially what I read here is that your bed is too small for the three of you to comfortably sleep ...... That would suggest one either finds a larger bed to sleep on or smaller people to sleep with. The larger bed seems the logical choice.
It sounds like everything else is going really well ..... good luck