elisa test at 6 weeks

hello i'm from malaysia.i had short (about 1 mins)oral sex (without condom)with a lady in 27th jan.after 3 weeks i got fever and flu(3-5 days),it's never happended again till now.
i did elisa test(generation 1 or 2) on 11th march(from 27th jan till 11th march=6 weeks).it's showed negetif,but the doctor ask me to come back after 3 months due to the window period.
1. does 6 weeks mean from the day i had sex(27th jan to 11th march) untill the day i did blood test?
2. i very worry it would turn to positif after window period,is that often happen?
3. what's different between elisa generation 1 and 3? what's the window period for them.
4. is my calculation of  6 weeks right(27th jan-11th march).
5. what's the WHO recognize for the 6 weeks?
thanks for answer.

[oldskool80]

no risk from oral sex...

[Mitch82]

Oral sex is not a risk for HIV