Does the effectiveness of morning after pills weaken if i've been taken it more than a few times within a month?

Yes: Emergency contraception is for emergencies, rather than regular contraception. Its around 80% effective. Using it multiple times in the same month increases your chances of pregnancy. If you are using it like this, its best to switch to a regular birth-control method that is more effective. Regular birth control pills are 95-99% effective. Best wishes.

No: However, you should consider using consistent contraception if you have had to use the morning after pills a few times within a month.