Is my ex legally obligated to tell me what's going on with our kids?

My ex and I have been separated for 13 years. We were never married and we have 2 kids together. I had the children living with me full time until 3 years ago. I had hit big financial trouble and suggested that the children live with him. It proved to be a very stupid decision. While my ex will let me see the kids whenever and since they are teenagers, they have their own phones. Here's the problem. My ex refuses to keep me updated. My daughter invited me herself to her middle school graduation and wanted me to help her get ready for the formal dance. It ended up in a big fight between me and my ex because his new girlfriend didn't want me in the house because she wasn't expecting company. My son has been grounded for a month for poor grades. The problem was, I only found out his dad took his phone after me trying to find (text) my son and getting no reply for 2 days. I finally had to ask my daughter what's going on. Then my ex allows my son to take a week off of school to go on vacation with his grandmother, while he's still grounded and without saying a word to me. I'm at my wit's end! My son is graduating high school this year so next year, we will only have our daughter who is in high school.