Married, pregnant and stressed

Hey ladies I hope you are all okay? Anyway I'm 22 and I go to university and not working at the moment. I'm married and have a 1 year old and have another baby on the way, which will be born in November. My husband is 25 and his been messing about once again. Before we had our 1 year old and got married he was talking to his exs and talking to other women and was on these dating sites etc. I found out after we had our child and when we got married, he told me he will stop what his doing, but he continues to mess about. Now I'm pregnant again with his second child and he is still messing about with these women again and acting like his single. He has women's numbers saved in his phone not saved under their name and his still on these sites. I don't know what to do anymore, sometimes I just want to give up. He continues to lie to my face and lies about his whereabouts. He tells me that he loves me and I've all what his got etc but if I really mean the world to him, he wouldn't be cheating on me. Honest to God I don't know what to do. I do love him and I want him to stop what his doing but I doubt his going to stop because his still been messing about after all these years we have been together.