Build your own loft bed

use 4x4's for the legs cut to the height you want you bed to be (don't for get to account for the thickness of your mattress)

Use 1x4's  as you bed support space them about 2" apart. Screw 2x2's to the inside of the frame 3/4" below the edges so the lats are flush with the sides of your frame

attach a 2x4 in the middle lengthwise at the same depth for additional support

optional: a fold down laptop self, so you don't kick it off the bed when you're not using it.

 Use 2x8s for the framing. I use bolts to attach the legs so I can take them off and move the bed. Though often it is needed to build the loft bed on the spot. For cross support I uses 2x4's about 2' long cut on 45 angles. I  do  a complex notching system for mine but you could just screw one end on the inside  of the frame and the other end strait into the legs.  My loft bed is only four feet off the ground, but if you want to make you're high enough to walk under, I would use longer cross supports to keep it from wobbling. Depending on how high you make it you may need to build a latter or use a step stool to get in and out of bed.