I had LASIK surgery about 3 weeks ago. My eyes started getting really itchy these past two days.

Sorry to hear about your troubles.There is too little technical detail in your post to even begin diagnosing the problem.You could have another problem unrelated to the laser--like a retinal detachment or cataract.You could have corneal scarring or ectasia. You should ask an ophthalmologist to ...

SMILE does take more time for some patients.  Some eyes will respond with more edema (corneal swelling) than others.  Be patient.  Know that if you didn't get your best result from your surgery, touch up procedures are an option for most patients.  

I would see the surgeon who did your surgery so this can be managed expertly. Conjunctivitis has many causes. Some can create immunologic changes that could affect the clarity of your vision.