Recently I have had a lot of ongoing stress in my life that has caused me to behave very poorly towards the people I love. If I stop and really look back, I think I have always struggled with my mental health a bit. 
I’m starting to think that I may have BPD or some other form of depression. This is probably the first time in my life that I have really looked at myself and how I have acted and thought that I may seriously need help. 
I have been very irritable and angry over what should be not a big deal. I depend on my SO for a lot and if she gets some details wrong I make her feel terrible for it. I have a problem with being jealous of my few friends and feeling like I am being left out. Even if I know I am not intentionally being left out, it kills me inside to see a my friends doing things without me.
I have experienced some really depressed periods in my life, lately lasting more than a couple days. 

What steps should I take to get help and/or to find out what is wrong with me?