I feel like a horrible mother!

I'm currently pregnant with #2 and I have a 3 year old at home who I love to death! I have always struggled with depression and anxiety and since becoming pregnant my anger has been off the charts! I am really short with my son and tend to yell a lot for very trivial things. I need help with this, but obviously can't really take the medication I'm sure I need right now...what do I do?! I don't want my son to hate me! He deserves more than what I am giving him right now....