I think other have said it. With our conversion upstairs at present we had wondered if chipboard would be good, laminated over then rugs scattered. The carpenter and joiner both gasped in horror. Even the best quality treated chipboard is a liability as far as they are concerned. If painted, most paints burn if they get hot enough and laminate gets as hot as hell, in fact wood is less hazardous. If treated, varnished or painted as we shall with pigment, linseed oil and turps paint it only slightly more flammable but many times less likely to be damaged by water in the event of it ever getting wet, always a risk at the top of a house as yours appears to be. Marine pine, medium knots if you don't mind them, does not cost a fortune. I have just done a 12m² floor, small I know, but under €200 including the stuff to paint it. The boards below boards would give extra soundproofing, some insulation and a quieter floor. Laminate might sag with the chipboard when it eventually starts to give.
You also appear to have put it in in lines. To be a bit sounder it should be staggered which can be every other line aligned or absolutely no alignment at all. The stuff expands and shrinks a bit too. A partition wall I put up with the tongue and groove joints tight buckled when high humidity was followed by hot weather. A floor with a bed(s) on it has that weight plus whoever is in the bed, plus other furniture presumably putting weight on it. Weigh up the pitfalls all contributors have mentioned anyway. Our two woodworkers explained it would cost us more in the long run because sooner or later it would need to be replaced, that could have been sooner.
We also asked the people building the house in front of us when they were here, the husband being a woodworker and building the entire house himself. We saw the floor was entirely chipboard, but he explained that joists and boards with insulation between are going over them, so in effect they are a ceiling. He would never dream of a chipboard floor either.