Why Lie!!??

Now I'm only venting, because I don't bring it to his attention. I just don't understand why does he have to lie. My ex intends to lie to me about a few things. He'll some times lie about how he's getting off late from work, but will instead go do something before picking our daughter up. So he won't pick her up till the evening. Most recent lies, Were, that he was going to Florida. Well, we agreed that I would let him take our daughter if he went to Austin. He did just that, but instead told me that he went to Florida. He could of told me that he didn't want to take her, I get it.. He went with his girlfriend and her daughters. This last weekend, It was my weekend. But he asked if he could have our daughter, since there was a party. I agreed, because he some times let's me have her on his weekend, If I have an event. Okay, Weell it wasn't a party!. He had a family day with our daughter, his girlfriend and her daughters. Now this might sound like I'm being jealous, or you guys might ask. What's the problem? Well, My whole thing is, Why lie to me!? there's no need to lie! I know about this woman, From my understanding, He's already had our daughter around her. And not once have I kept her from him! Ssoo whhyy lie!?