DH have been together for 7 years and married for 5 and have 2 DC's. Last year we separated because we'd grown apart for various reasons and remained on very amicable terms. So amicable in fact, we have still been sleeping with each other off and on and this led me to have hope for the future.
While we've been separated, we've still seen each other practically every day and he helps out around the house although we still said we would divorce as soon as feasible for us (mainly because I said that for it to be a fresh start, it really had to be a fresh start with the marriage behind us and work together on the future)and he would always tell me he loved me and hug me and give me kisses.
A little while ago a new woman came into his scene, we'll call her Ada and he seemed very taken with her so I stepped back a little, confused as to what it was he wanted. Up until last week, he was spending every spare moment he could with her and I admit to being jealous about it.
I asked him if he would consider giving the relationship between us another try and he said yes and would end it with Ada. Since that time though, he has lied to her about why he was ignoring her, lied to me about what was said to her (proof was in his e-mail account that he left logged in on my computer) and on the day he was supposed to break it off with her, he walked with her to her home (something he'd never done before) even though he said he had no feelings for her.
He is still receiving, and answering texts from her and gets very angry if I try to mention her, going so far as to defend her honor when I called her a derogatory name or seven 
. He has also suddenly started witholding the affection he was showing me up until about last week.
I really want to make this work and am determined to give it my best effort, go to counselling with him if required and change some of the bad habits I'd gotten into but I can't shake the nagging feeling that he's still seeing her while seeing me.
I really don't want him to be with me if he wants her more or if he has only decided to try again because of the children and I certainly don't want to be with him if he's just playing a game with me but I don't know how to get him to open up to me about everything without causing a massive argument. He's not a very talkative person to begin with and doesn't do very well when dealing with talking about feelings and emotions to begin with.
Does anyone have any idea as to how I can do that without it all blowing up at me? Is he still seeing her do you think and just playing a game to see who he likes best?
Any advice would be appreciated right now :)