Having trouble communicating due to extreme shyness

I have trouble coming up with what to talk about like I have to think 100 times what if i say this or what if i say that what will the person will think. My shyness is even worst with strangers to the point I cannot even say hi or hello out of politeness due to shyness. I mostly then come off as either arrogant or mentally challenged to others but its just simply my shyness combined with socially anxiety which makes me come off as closed off. I have trouble communicating even with my parents now. Because of this I've always been lonely and had 0 friends.