Texas Based Situation

I live in North Texas. My Ex-Wife lives 100 miles away. I pay my Child Support on time and have for the whole time. Everytime I turn around she keeps making up new obsticles. The school where my Son attends don't contact me when he is absent. He is 7 and Daughter is 4. The Mother-Inlaw lives about 10 miles away. I have always been nice and tried to get along with the overall situation. But, it seems that my Ex-Wife thinks she can just go behind my back and do what she wants to with the kids. We are in joint but she is the primary. First we had a good agreement then it just kept changing all the time. NOw... she says kids cant stay at my house because i don't have seperate rooms. Then a buddy of mine who is a Father himself moved in cause he has came back to Texas and Ex-Wife says. Well, you don't have enough rooms for the kids and you have someone living there with you. It's a Man! She isn't married and been living with a man for about two years now. They have multiple people living in the house. But, I'm never told when they go to the gmaws. She pretty much tells me when i am going to see the kids. The kids were at their Gmaws for 3 weeks and I got to visit with them from am/pm. She brought them and picked them up and charged me for the gas to do so and Ex-Wife..not the court.... was telling me they couldn't stay over night. I couldn't bath them....a lot of stuff that didn't make sense to me. And just this past friday without telling me or informing me. They were sent back down here to the Gmaws house and