Hello fellow mama's! So my oldest son seems to be developmentally delayed and he won't be able to…

Hello fellow mama's! So my oldest son seems to be developmentally delayed and he won't be able to see a behavioral therapist for another 3 months and is on a waiting list for a speech therapist ( recommended by pedi) Any other mama's going through or been through this that can offer some tips and tricks? Maybe some exercises I can do with him in the mean time? A little background, he just turned 3 last week. He's not speaking at all but can understand if i ask him to do something. (ie. Throw this in the garbage, go sit on your potty, please don't yell, ect.) It seems he trys to sing along or make out words but then gets frustrated and crys. It hurts my heart to see him struggle and makes me feel like I failed him.