Yes, you should be clear of the heroin by Wednesday as the drug only stays in urine for around two days (metabolite traces can remain for a maximum of four days).
In your case, it may show be detectable for slightly longer as you took quite a large amount, but given the time scale you should still be clean come test day.
There are factors to consider though: It will depend on your weight, age, metabolism etc... but in my opinion you should be safe.
It's a pity that you relapsed, but well done for coming off it in the first place, hopefully you can continue to be heroin free.
I'm not here to lecture about drugs and I know you are aware of the risk factors, but you have proved that you have the strength to come off it and there are certainly more benefits involved in not taking it - financially if nothing else! :-)
