Secretly using facebook?

After i married my husband, which was 5yrs ago, he didnt want us both to have fbook. Cause he acted like it destroy marriages. He also said he doesnt like guys checking me out. So, we decided to deactivate both our accts.

2yrs into our marriage, his ex wife messaged, and told me that when they were married, he created secret email accts, and were using them to create a secret fbook, talking to other women, and checking them out. However, they both were using fbook. She told me to watch out, cause she guaranteed hed do the same to me.

I didnt think he would do that to me, but yesterday he was touching his phone. And i took a peek at it, i saw that on his recent app search history, showed fbook. The fbook app even had a silver circle on the top right hand corner.

So now im thinking that hes doing what he did to his ex wife, to me. Ive asked him and he said im being ridiculous, to quit looking for problems. He did not let me see his phone.

Idk, i feel like i need to snoop, since hes being so secretive w his phone. And i feel like hes secretly using fbook.

What do u think i should do?