Can I increase the ceiling height in my mobile home?
No. Your roof is built to minimal height standards for cost, insulation, travel height, wind handling, etc. You basically have ceiling joists, a relatively small space for insulation, and the roof. There's no extra height available there. You will need to raise the upper roof surface to make room for livable space below.
Here's a short list of things that need to happen to raise the roof in part or all of your home:

Roof demolition
Wall framing
Roof framing
Plumbing vent extension (if present)
Utility vent/flue extension (if present)
Roofing repair (shingles or membrane, edge flashing, penetration flashing)
Electrical wiring extension/reconfiguration
Wall and roof insulation &amp; vapor barrier
Exterior siding &amp; soffit
Drywall hanging and taping
Wall and ceiling texture and painting
Building permits
Inspections

Whether this project is appropriate for you is entirely a matter of prerogative, budget and legality and not ours to say.
One other consideration is that mobile homes tend to be subject to wind damage (tipover). Raising the height of yours exacerbates that problem.