I feel stuck

I’ve been in a relationship for going in 8 years. We live together and have 2 kids and one on the way. Last year around this time I found out he cheated on me multiple times. I have tried to work on myself and in the relationship. Prior to this he’s cheated before. I again at that time chose to stay because I love him and for my son at the time. I had my share of wrong doings but still never justified his actions. I’ve never cheated. Recently since this January I’ve gone through his phone and he’s been flirting and talking to other women. He admits he has a problem but then also doesn’t try to help me trust him with him being honest to when he has female friends at work. He’s reasoning is because I will be upset or bothered by it. I told him I wouldn’t care as long as there are boundaries. My main thing is be honest when I ask. He refuses to be honest and always gets caught in a lie. Last night I felt like this was my last straw. He said he was going to work overtime, but as the night when on I felt he was lying. He’s off work at 3:30pm and it was 11:30. I know there is no way he could stay that long. He works for IT in a hospital. When I called me back the background sounds were odd. So then I told him to screen shot his location on google maps. He said ok and hung up. He never did it. I know that is ridiculous, I didn’t want to even have to say that. I knew he would do it if he was telling the truth but of course he didn’t. That’s how I knew he was lying. Anyways, once he was almost home I told him I knew he was lying and he for once fessed up the first time around. Said he worked a couple hours over but ended up going to a bar with coworkers because a female in a different department was her last day of work. Some guys from his department went to. He said he didn’t tell me because I wouldn’t be comfortable with him going. I told him, “ So you rather be caught in a lie than tell the truth?” He feels either route he may go I would still be bothered. I told him well you always lie so you would never know how I would react. I may be uncomfortable at the beginning of your honesty but as you continue to be honest and forward with me about friends I’m sure I can learn to believe and trust you, but he never does that. I also went through his phone and again talking to females at work in a flirtatious way. One knows he’s in a relationship and one doesn’t. Other thinks he’s just a single dad. I’m just fed up. He’s not going to change. I’m tired of being treated this way. I’m just sad for my kids who are 4 and 3 and I’m 6 months pregnant. I’m a stay at home mom. Haven’t worked for 4 years as an LVN. My 4 year old is autistic and I’ve mainly stayed home more so to help him. I just don’t know how to separate myself from him. I just feel stuck. I feel like I have to stay living together until I get on my feet after having the baby which isn’t until august. Living with someone you are no longer with and love I feel like it’s torture and have to put a front for my kids to an extent so they’re not affected in such a negative way with the transition. Only option I had is to live with my mom but there is definitely no space for all of us and I couldn’t put that stress on her. I feel like I just have to suck it up until I can make a living change.