>>600179
Check out 1 Corinthians 11:27-32.
We must have confessed before having communion, otherwise we do not "eat and drink" the Body and Blood but rather "blaspheme" it.
Not only is it a mortal sin in itself, but it's also probably the most damning one you can commit. The consumption of the Eucharist is a sort of small "last judgment" - if you eat and drink while in communion with the Church, you grow toward divinization and sanctification, but if you eat and drink while being in a state of mortal sin, you are already condemned.
But do not despair. God allows us to stumble but not to fall. That you feel disgust at the sin you've committed is already proof that God is giving His graces to you. Examine yourself, repent of your sins, go to confession, and you can have communion again.
If you've been regularly having communion while in a state of mortal sin, that would surely explain why your spiritual growth was hindered enough that you committed sexual sin even after 6 months of abstinence. I'm just speculating here, though.
This is an Orthodox link, but it might help you for a first confession anyway.
http://antiochian.org/orthodox-prayers/self-examination-confession