6 month old suddenly crying a lot?

Hello everyone! I'm a FTM and I need some advice. My son recently turned 6 months and he seems to be going through a LOT. He's teething, his poops have decreased in number, he refuses to do tummy time, he arches and locks himself up when I try to sit him up or change him, he's waking up more, wants to eat more, crying when I walk away, thrashing at night and he has suddenly started BAWLING randomly throughout the day and when he gets tired.

I have NO idea what is going on with him. I don't know if he's testy because his mouth hurts or because he has to poop or what. I'm at my wit's end, I'm so tired. He's normally such a happy little guy and he's been so difficult the last few days. He doesn't want to be our down and at the same time he fights me when I hold him. He has his 6 month checkup on Monday so I'll be asking about it then, but does anyone have any idea what this could be? I thought he went through his sleep regression already, but maybe this is it? Any insight would very much be appreciated.