As ashamed of it as Jake is, his first thought after cheating isn't about how wrong that was. He doesn't think of how much he just hurt Marley (even if she doesn't know yet) or how he probably ruined the first good thing he had going for him.
His first thought, is how pissed the other New Directions are going to be.
He remembered when Blaine cheated on Kurt. He remembered how livid everyone was. How Tina screamed at him, how Artie kept rolling over his toes in the hall, all the names Unique spewed at him (Kurt was her idol after all) and how Finn had basically acted like Blaine didn't exist.
Because he had hurt Kurt, and even though all of the Glee clubbers were younger than him, all of them had looked at Kurt like he was a perfect little flower petal that they needed to protect. It was a state of mind they had all developed after years of locker shoves, and dumpster dives, and slushies to the face. Kurt was their baby penguin and he was theirs to protect.
And even though Marley was new… her innocence had instilled that same state of mind over her. Defend, protect, kill anyone who would dare hurt that delicate little angel on Earth.
So Jake waited for the onslaught. He waited for the hateful names, for the glares, for the wheels over his feet. He was terrified, and he was more terrified of that than of actually facing up to Marley and seeing her tears.
It was terrible, but it was true.
He hid in the lighting booth of the auditorium, too scared to leave. He stayed there for hours. He heard the screams and shouts of outrage as Kitty told them what he had done. (Marley had run to her, not sure who else to tell and just needed a shoulder to cry on)
He waited and waited, and then there was silence. It sounded like everyone had left, given up their search for him. By that time, his heart had finally caught up with the terrified part of his brain. He saw Marley's face as she begged him for it to not be true, to tell her that Bree was lying, to have not cheated on her.
Kitty texted him a recording of Marley singing Wrecking Ball and every word was like a knife to the heart until he wasn't even sure how his heart was still beating it was so tightly constricted. He couldn't breathe and his curled up position wasn't helping anything, but he couldn't bring himself to move. So he sat there, in agony, tears streaming down his face as he cried for the first time in years.
Then the door opened.
He tensed, not knowing who to expect or what to expect them to do. He wished he could just sink into the floor and cease to exist.
He saw his feet first. The familiar boat shoes with no socks and the bright red skinny jeans. He didn't say anything, just crawled under the table and sat beside him, placing a strong hand on his back.
It wasn't the same, and Jake knew it. Blaine had cheated because he had felt unwanted, Jake had cheated because he was horny and angry with Marley for not putting out.
But this part, the mourning of the lost relationship over a loss of proper brain function, this part, he understood. And so he stayed there, holding Jake when he finally shifted over, and let him cry.