Hi, I need some support/help/...

I'm a 25 y/o guy who suddenly suffers from anxiety. 

I had a depression a couple of years ago which I came out stronger but now I feel like I'm on the verge of a new one...

I just finished school and got a nice job. But idk why, I think it's the change and the new things etc. but it freaks me out. I suddenly start to overthink about everything (that I'm not good enough, that I will fail, that I will disappoint them etc.). Last week, when I came home from my second day at work, I just couldn't stop crying because of those fears. I have a girlfriend which supports me etc but I even worry and overthink about if I'm going to lose her because of how I'm feeling atm..

I just need some help or advice..