Ph very low 3.5

[alex-76]

So, i'm very sure i made a big misstake a long the road.

Let em explain.

i decided to have 20 gallong of mash. 70% rye 30% malted barley and whinter wheat. Checked the water PH 6.6
I started to cook it and got to 140 - 145 for an hour.
I let it cool down, took for ever to get to 90F. So i checked the PH and it was 3.5 and the mash was bubbly
so i added sodium bicarbonate and i added little by little. But i ended adding a lot and only got it to 4.5
I think if i add more i would probably have a lot of sodium bacarb when i distill. Doesnt it fall at the bottom before distilling it?

Now, should i add more sodium bicarb to get it to 6.5 or 5.5?

What can i do?
and how can i prevent this to happen again?