???
No exact dates are given for when Tiffany and Steven (Jessica and MC's dad) met, as far as I recall. The only dates we have are the ones of the past (20 years ago), and present. And Tiffany being pregnant 20 years ago, lines up with Jessica being 19.
We also mostly know for a "fact" that Jessica and MC share the same dad, because they seem to have shared memories of him. No mentions of "different dads". It also kind of rules out the "MC is his own father" theory, at least for now, seeing as we haven't gone further back BEFORE Tiffany got pregnant. But that can obviously still change.
I guess it is possible that Steven just adopted Jessica, and that's why Eric is never mentioned as the dad. But I somehow doubt it, as that'd make both Tiffany and Steven liars. As it stands, we really have no real reason to doubt what we've been told so far.
It's still very much a possibility that MC is the father of most of the girls he interacts with in present day, though.