I applied OPT in May 7th and wondering how long will it take? Will it take longer than 90 days?

I doubt it will take that long. It is usually around 30 days or so, give or take!! I applied for mine a the end of Decemember and I got it Feb 16th. Once you have it , it should be valid for 365 days from they day it was processed, not the day you applied