I'm 31 weeks and I have bad stretch marks. Well naturally they itch when I stretch, but I try not to…

I'm 31 weeks and I have bad stretch marks. Well naturally they itch when I stretch, but I try not to scratch to much for risk of doing more skin damage.

Well here lately I've noticed that even when I go to put a shirt on that they are sore and feel irritated... And they turn a dark purple and around them are red.

Is this normal?