Can I ever trust him again?

Been with my fiancé for 3 years now. About a year and a half ago I found out that about a week after we started dating,he joined POF dating site.

Not only that, I had suspicions when he never ever left his phone unattended.

When he thought it wss broken he left it at home and went to work. I tried fixing it...and did! So, I decided to look. When I did I found soooo many dirty messages vis email, text, WhatsApp, FB. I confronted him and all hell broke loose!

He had been flirting, sending cock pics, receiving explicit pics from other women. Chatting to ex's. I know of 2 times he met with his ex behind my back.

Basically, after so many 'discussions' we are now ok. I am happy. But something deep down says I can't trust him 100%...or is it just paranoia? After all he did propose to me and wants children with me...