Im think I’m getting cheated on

I can’t find any other answer. I’m going nuts.

Lately my bf picks up fights a lot. He makes a big show out of nothing. This happens every 2 weeks. He has a phase where he’s happy and doing so good then his mood changes drastically.

For the month of august and September, he’s done this. Every 2 weeks he picks up a fight. He just did it again, he goes silent for 3-4 days.

Idk what’s going on.