So upset and frustrated

I need to vent or something, so long story short my son is 2 1/2 and we realized that he is speech delayed , he doesn't say alot of words he babbles but he gets so mad and yells ! Somedays it's constant , I'm 30 weeks pregnant with my 3rd child and I'm beating myself to a pulp that it is my fault because he came at 35w5d , I'm terrified I'm going to be dealing with the same thing with this baby bc he's coming at 36 weeks , I'm doing everything I can to push it to full term! I have read and done research that premature babies can have delays due to being early .

Lately I am so frustrated I cry all day long and just feel so down and upset that it's my fault he has to deal with this ! It doesn't matter what I do I cry hyperventilate bc I know I caused it . I gave my son this because body wouldn't keep him in long enough, now I have this baby coming and I can't even enjoy it bc I'm TERRIFIED 1 he's gonna end up in the nicu like my other 2 ( I have a 6 year old daughter) and then on top of it , he's gonna have these issues like my son . It's not that I'm upset he's speech delayed I'm upset because ITS MY FAULT !

We put our son in to Pre-k to see if that would help him grow , you know being around other kids and then doing language learning etc... well that went to hell , the teachers didn't want to deal with him they complained constantly compared him to other kids in class, mind you we already had him evaluated , hearing test and started speech therapy where they come to school 2x a week to work with him etc informed the school of what was going on and they still allowed him to enroll. So now he's out of school and I am terrified how am I going to handle him and a newborn ? I will figure it out I obviously have no other choice but am a horrible person for even feeling the way I do ? Or even complaining about it ?

I suffered post Partum depression with both before and I was put on Lexapro but being pregnant you can't be on anything and I'm scared to death to even mention it to my dad bc I don't want them thinking I'm crazy for even thinking I'm depressed during pregnancy and just don't know how to cope or pull myself out of this , I want to happy and want to able to accept all this but I can't. It's like the unknown is so scary for me . Please don't judge me or think I'm a terrible mother for feeling this way. I just am at a total loss as to what to do how to feel or even how to express everything