Lost custody

I’m 21 and have two kids. I lost them because of my ex and his now girlfriend which is my ex friend they both lied. I couldn’t do visits because it was going to cost me $2500 and I had no job at the time. Well, they got custody and told me they didn’t want child support from me. Now they do. She also thinks I claimed the kids for taxes which I didn’t and apparently they found out who did and they are saying it’s my grandma who is very old, doesn’t even work and gets SSI. No one even has the cards except for me and I had them hiden it’s still hidden there. I told her to leave me alone and she’s like have fun paying child support and other expenses out of your ass. All she does is threaten me with child support and it’s making me stressed and depressed. I haven’t even seen my kids since December because of her. Can they do anything? And I even asked her to see my kids and she said no and saying I’m a bad mom and now my kids who are 2 and 8 months old both have anxiety when I don’t even think they can have anxiety. Please no judging I don’t know where else I can ask this..