It is evident that he debated the fact whether the child was his but in his nightmare sequence at his dad's apartment, 'Janice' proclaims that Matt could very well have read her mind and known the truth of the baby's actual father.

What I want to know is why Janice preferred to lie to Matt in the first place if the child was his and why Matt chose to leave the two of them even after he allegedly knew the truth?

Any theories or speculations?

I personally think that Matt was unconsciously following in his father's footsteps and unable to face the fear of bringing up a child as his was without his own father during his childhood. He probably thought that he would not do a good job as a parent but inadvertently fulfilled a self-prophecy by leaving his very own newborn child.

it could be to do with his powers aswell, he's more concentrated on his abilities as to why he has them, who gave them to him
not that bothered about his family

Maybe Matt left her for the FBI chick ....lol
But i think we'll get to see that in ep.8 "4 mnths ago"..i hope

Hopefully in Episode 8 there will be answers.

I am very sure there will be but that is still a long way to go. For now, I seem to be tossing between the fact that Matt left them out of fear of bringing up the child which he allegedly did not know was his or just plain protecting them from forces yet unseen.

i doubt this theory but maybe like in the future episode from last season, he's actually protecting them somewhere and just used the 'divorce' story as a cover up..? but yea like i said, i doubt it..

since "he abandoned his wife and kid" was part of his nightmare, I think the divorce is not a cover up. Its a convenient way to get rid of a story that wasn't working though!