There can be many reasons why you get pimples after exfoliating.
1- You may be over-scrubbing your skin, which can irritate it and lead to breakouts.
2- You might be using a product that's too harsh for your skin, which can also cause irritation and breakouts.
3- It's also possible that you have sensitive skin, which can react to even gentle exfoliation by becoming inflamed and developing pimples.
If you think any of these might be the case, try backing off on the exfoliation for a while and see if your skin improves.