My son is on 18mg of stratera for 4weeks now. Now he is crying about everything and his adha had not improved. What should I do? He has highs n lows

Talk to the dr. Stratera is a non-stimulant that is chemically similar to an anti-depressant. I would recommend a change or reevaluation of the medication. I would also suggest starting individual therapy if the depressive symptoms persist.
Call! Get a phone call in to the prescribing doc and ask to stop the med (or just do that yourself). You will likely need another appointment to discuss a different treatment plan.
Talk to your DR. If after 4 weeks, you have seen no improvement in your sons adhd on the strattera, (atomoxetine) and he is crying all the time, his medication may need to be changed. If it isnt working for the adhd, the dose may be too low. My only concern in him staying on the medication is his crying and emotional lability. A higher dose may exacerbate these symptoms. Therefore, discuss with your doctor.