Thanks for your responses so far.
I am pretty sure that I am suffering of a depression, if it's a postpartum depression or not - I am not sure.
I was dealing with depression in my life before: this feeling of guilt and hopelessness, just anxiety and very dark thoughts.
I feel depressed like this for a couple of months, after a traumatic birth, after a very exhausting time, when I went back to work (then I got laid off, but that's another story) and some chronic pain issues. What it makes worse, is that I don't have family around. My family is in one country in Europe, my husband's family is another country in Europe. So, I don't have support here. I have here a mom's group, but I have the feeling, that the other moms just have no problems. Everybody is always in a good mood, they never talk about problems (but I also think that there is a difference of mentality and communication between European and American way of life...). We are not very close, but see us on a regular basis. 2 of them also watched my son for a few hours, when I had to go to the doctor.
What I will try to do: go back to my family doctor (I just did the test in the sticker, and I had a score of 65), and I will contact a few of the licensed social workers. Maybe they can start a therapy and give me a prescription.
Thank you very much for your input.