Baby suddenly crying a lot and being difficult?

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, 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.