Take off the hood, and any other accessories which may be getting in the way. Shoot a roll of C41 film and get it processed at a different lab to usual. This will rule out any processing issues (either with you, or your lab).
If you can dry-fire the camera, try firing the shutter with the back open, and see if the shutter stick at all. If it's visibly underexposed, it may be visibly sticking too.