Way to find out cheating

Does anyone have any clever and smart ideas on how to find out if their spouse is cheating apart from looking in their phone. My husband chose to live apart from me but pops in and out as if I’m a hotel at a separate home from me and the kids and barely text me otherwise. When he’s here he puts his phone legit under his pillow.

He all of the sudden claims his texting on his service doesn’t work due to an iPhone update and uses WhatsApp to talk to me. Has blocked me on fb and Instagram. Claims he isn’t doing anything shady but all his actions are in fact shady.

Any ideas?