I need help!!!!

[Kat1]

Please can someone help me with email issues. I'm a total technophobe and don't know that much about android apps etc... However I'm losing my mind with my partner. He is very good with tech and I'm sure he is hiding something. He has an extra phone number on his Web messages app, receives umpteen spam messages and emails from porn sites and even though they're addressed personally 2 him he swears he doesn't know who they are. He also downloaded APK apps so he can say he doesn't have access to any social media apps... Why does he have a separate number on his phone and why does he have conversations with girls on Google chat that only have email addresses, and u can only see the spam thread by going through a windows browser and html format on his phone? He happily gives me his phone if I ask for it but I'm beginning to think he has another phone hidden away from me so I'm not sleeping anymore as I'm constantly on edge or checking Internet archives. Am I missing something or am I just going mad? Plz someone help me. Thankyou