can full custody be regained?

When my son(raylun) was ten days old me and his dad(dustin) signed temporary custody to my mom bc we were active addicts. It was completely voluntarily. It was supposed to be for us to get sober then custody be returned. 4 years later im over 2 years sober and havent seen or herd from dustin in over a year. Hes no longer in the picture. Ive been with my amazing boyfriend(cody)almost 3 years now and hes went above and beyond for my son. I hav done everythin asked by my mom to prove myself including random drug test that she still gives me. Ive passed them all. My mom is an amazing mother and i truly appreciate her making my sobriety possible and steppin up formy son but this passed year has been a struggle. My dad is divorsing my mom and its reallymentally gotton to her. She has made several horrible desicions for my son and there have been anumber of insidences that have happened under her care. She works all day then is gone at night now. Its no longer in my sons best interest to be with her for a number of reasons. They live inmy lil sisters basement. I am over 2 years sober,have a home, 50 acres, 3 vehicles, all the essentials and a great support system. Im in a muchbetter pla e and beyond ready to step up and raise my son. Trouble is my mom has lost everything with her divorse except my son. He is all she has and she isnt letting go. Its not like she wont see him regularily bc she will. Were a very close family. But with everything thats going on in her life now, she isnt raising or taking care of raylun lile she should. And evwn worse she dont realize it. Id love to get an outside oppinion. We made guidlines in our custody agreement and ive more then met them. Can anyone relate? I could understand if i hadnt changed but ivegot over 2 years and mymom randomly drug testing me (still)has proved it. Lile let me raise my son. My rights weren't took from me. Me and his dad voluntarily signed custody to my mom. Its stated in the custody agreement if im able to properly care for him custody could be returned. Ive been actively in my sons life. Until this last year i provided for and raised my son since he was born just under the safty of my moms home. My mom is my biggest trigger so i had to move on my own. I have 50 acres,a home(were raylun has his own room, bathroom,play room, ect) 3 vehicles, stablity,over 2 years sobriety,an amazing support system. Im in a much better place now and my mom on the other hand isnt doing so good. My dad is divorsing her now which has caused her to have like a mental break down or mid life crises? Several insidences have happened withmy son under her care in the last year, she is gone allday working then gone every night(which means shes NEVER home to raise raylun and instead dumping him on my youngest sister to get to school,feed,bath,get to school,ect and hes with me everyweekend and when there isnt school)
She lives n my sisters basement,she jus now working for the first time in almost 5 years(since raylun was born),she starts night school soon so she really wont be around to raise him,she still hasnt got him a dr and the only reason he jus went to the dentist for the first time is bc i took him. I am more then ready and prepared to take back custody. I didnt mention most of the insidences bc theres to many but i can if needed. She tries to say ive never help with him that shes done and got everything but kinda dunny she didnt work. I bought the $350 bed she has and refuses to give back, the $1,500 swing set she also has n wont give me, almost everything he has either i bought, was gave to me from friends n family, and a few times my dad had to help. He jus got over his second really bad sickness n fever that she refused to take him to the dr over. She wants to keep him but doesnt want to put his needs over her own. Im so grateful she helped me get sober but now the tables have turned. She needs to figure out her life and focus on her and i want to raise my son. Every single day. I want to bathhim, take him to the drs,school,ect... and am more then capable of doing all these things. Ulike her holding the title of custody but completely ignoring the responsibilities. She refuses to sign him back over and i dont have spare money for a lawyer or court fees. Please give me advise or and outside opinion and comments on my situation.