5 month regression ?

Is a 5 month regression a thing or is my baby perhaps teething ?

So my 5 month baby, almost 6 months on the 20th has had the shittiest sleep. He is restless at night, waking every cycle meaning very 40-60 min. & he just seems exhausted. I feel so bad for him. Even cosleeping is not working.
He just seems uncomfortable, tossing and turning and whining with his eyes closed.

We are getting use to the sleep regressions and every week being so different, we’ve just accepted that it’s not always going to be perfect, so it’s not as bad on us.. but we are feeling it for our baby who just seems tired.

He overall seems happy & always smiling but his windows have shorten since the restless nights. He already has one tooth & we are assuming maybe another one coming ? We’ve given him Motrin that his doctor approved and still seems like it’s not working so if it’s not pain what is this?

As of last week I started implementing a schedule, sort of, since I also started wfh. The times range since he can be inconsistent but it’s helped with his naps, he goes down for them so much easier!!! But…… he still takes 30-45 min naps, if one is 1hr 15 min it’s a good day.

wake from 7-7:30 am 2 hour WW nap 1 9-9:30 am 2.5 WW Nap 2 - 12:40 -1:30 pm 2.5 WW Nap 3 - 3:30 -4:00 pm 2.5 WW Bedtime 7:30-8:00 pm

Since again he can be inconsistent, the times range so he sleeps/naps in between any of these times.

Anyways please let us know why we are doing or perhaps what we can do to help our poor baby sleep through the night or atleast have a good first stretch.