I'm 24 and I noticed my irection is not as hard for the past 2 yrs. And now it seems like the size is smaller when im hard is this happening. I workout?

See below. Do you have high blood pressure, diabetes, high cholesterol? Are you taking any medications or supplements? Are you using steroids to help bulk up when you workout? These conditions/meds can affect erection. See your fp or urologist to discuss the problem & options to help.
Not likely. Most likely it is not due to work out. Stress can do that. If the problem persists you should see a urologist.