Progression is about more than just adding weight to the bar. That's just one way of progressing. There are several other ways:
- Do more reps with the same weight.
- Do more sets with the same weight.
- Increase density. Cut time off your rest periods or use active rest instead of passive rest.
- Increase the quality of each rep. For example, explode the weight up better.
- Improve mental focus.
- Use intensity techniques: supersets, drop sets, rest-pause, etc.