What do you mean "3 weeks ago before period"? Do you mean you had sex 3 weeks ago and had your period after that?
If that's the case, it's unlikely you're pregnant, and it's likely the clear discharge is a sign you are ovulating again.
Sorry meant to say I had sex 3days after my period and now 7days late
So 3 day after your period started (so like 8 days after your period began) you had sex? That's within your fertility window, and sex at that time could result in pregnancy.
I'd take another test with first morning urine. If that one is also negative, it's unlikely you're pregnant and you may just have a late cycle.