3 mo. AND/OR 4 mo. Regression

So if you google "3mo sleep regression" and "4 mo sleep regression" it seems like they both exist. I believe my LO is teething and starting the 3 mo sleep regression. Has anyone experienced a sleep regression at 3 AND 4 months? Or is this just one sleep regression that has a range of onset? Really hoping that we don't have to do this again in 3 weeks!