Struggling with Dads diagnosis

My Dads MDS has relapsed three and a half years post allo transplant and I just can't get my head around it. I'm devastated and just can't stop crying. We found out yesterday from initial bmb results and will find out more on Thursday about the best course of action for him.... possible DLI or chemo injections to just stabilise the mds. The DLI could potentially get him into remission but I'm just terrified he is going to die. I feel like I'm drowning and I just want to try and get some perspective back somehow....