diarrhoea or teething?

Monixxx • Baby born March ‘19. TTC #2

My baby boy is 22 weeks old. Recently he’s gone from 2/3 poops a day to 7/8. Usually they are very small, yellow and quite runny. Also they SMELL so sour!

Has anyone else had experience of this? Reckon it’s due to teething or is it diarrhoea. He is exclusively nursed and hasn’t begun weaning or eating solids (although he does lick some of my fresh food like carrots/parsnips and broccoli) as NHS says don’t give solids till 6 months.