Funny thing, I looked into log system and saw the hint.
The problem is that I looked at "abstain for three days" and my first thought was "huh, looks like no lewds for three days for me". After many fruitless attempts I just continue playing, reaching to T'ris' public favors. Then, to remove annoying quests, I just looked into the walkthrough and realized my mistake. And T'ris, being herself, made it feel so natural having sex on the bridge first, THEN giving a blowjob to MC LATER.