What should i do when my man lies to me.?

Me and my man have been together for 2 yrs now and in the beginning everything was great. But now that he has a kid with his ex the lies just keep building up more and more... Like he still talkes to his babys momma like they are still together,wont even talk about the kid just things in there life.. i don't mind him talking to her when it is about the kid but when they talk about whatz up in there life it makes me mad.i tell him about it but he just tells me to shut up and im the stupied one.. Anyway the most resent lie was on fathers day his mother brought is kid down so he could visit with him which i didn't have a probelm with but for some reason he kept acting shady the whole weekend so i asked him if his ex was down here he sware up and down that she wasn't.. Well come to find out she was down here and they were hanging out (the whole weekend while i was at home)i just don't know what to do. I want to leave but im scared to cause do i love him with all my heart..Plse someone hel