I am a roof designer. Please get this looked at by a professional. You are most likely facing structural damages, leading to weaknesses in your roof. The most likely candidate is damage to the panelling overlaying your rafters or trusses or damage to the fascia/soffit boards.

The last thing you want is your ceiling joists going rotten/soft and caving in. This is unlikely, however you should still get this looked at asap as even the smallest changes can cause large deviations in the roof structure.

When you say there is no room above, there most probably is unless it’s a flat roof. Not a habitable room, but attic space. This space may contain your cold water storage tank or other plumbing which could be leaking and also be a candidate for this issue. Check your water pressure is as normal. Contact your land lord rigit away if you have one.