Had REVOLAX deep lip filler 3 days ago and my lips have gone back to original size, should I get different filler next? (photos)

Some of the initial effect of any dermal filler will be swelling, and when that goes it is common to feel that the lips are not as full.
I would go back to your doctor at 2 weeks after treatment for a review. The filler can be felt usually at that point to see if it is present. It may just mean you need more filler to achieve the look you want.
Sometimes fillers do breakdown quickly, especially around the lips but even then they would still be present for a few weeks.