Is it out of order to ask? ?

Previously had some trust issues in my relationship due to some emails I found saying along the lines that my man wasn't happy with me. A year on his only female friend and ex work colleague has been chatting on facebook. I made it clear I wasn't overjoyed but he has the right to be friends with who he wants. Problem is, he's always on his phone. I know he's been back on facebook chatting to her but when I asked him he lied and said no. Today I'm considering Telling him how I feel and asking to see his facebook messages. What do you think?