Your agent is giving you wrong information. You have to inform them of your marriage right away because it effects your points. You should recalculate your points now as a married applicant and non-accompanying spouse. You are good, if your CRS as a married applicant is still above the cut off score of the draw in which you received ITA. Otherwise, your application may be refused if your new CRS is lower than the cut off score, which is why informing them of your marriage is of prime importance.
Let's say you receive your COPR after 3 months. Do you have a valid explanation as to why you didn't inform CIC 3 months before when you actually got married? Hope it makes sense and you should raise a CSE right away without any further delay. Feel free to take opinions from senior members.