Last year I took my phd in applied math. Now I am 5 months into my first postdoc (different subject from phd but still modeling and some numerics) which is 18 months in total. Both phd and postdoc are in the same country, abroad.
A little bit of history: The first time (during the post doc interview) I was presented the project (which is in mathematical modeling) I was very excited and thought: let's do this. I was told that I would work in a group and have people to help me (including a phd student). So I accepted. The phd student proved to not help me at all. Not because he doesn't want but because he cannot.
In the first 2 months I did some brainstorming, read other people's work, found some possible approach and gave a presentation to the rest of the group about it (still nothing concrete i.e. no numerical results / simulations). When I actually started working on it (like writing equations and code) I started with a very simple case. The thing is, after almost 4 months I am still stuck to the simple case. And I am completely discouraged because I already have my phd! I don't understand what does not work (is it the equations? the code? me?).
The last two weeks I am so stressed, that I can't sleep, I cry for no reason and I have decided to go in the next days to a therapist. Next week I will talk to one of my 2 bosses and tell him that the final model I agreed to give them is something which is absolutely impossible for me to do because even if i find the right equations for the model, I need to code it (which seems too complex because the model is far too complex) and do that of course before the end of my contract. I used complicated codes during my phd but I did not develop them so as to have the experience.
I want to open up because I am tired, demotivated and stressed and I don' t want to do research like that. I am planning to talk to them in order to find a solution that works, otherwise I don't have problem to leave. I will tell them that if they are ok with it the most I can try is to continue working on the very simple problem I am doing now. I think that after such a talk I WILL have to leave (which does not make me very sad because I hate working under such conditions). I am also afraid one of my bosses (the group leader) because I have heard stories about him and a phd student that was in the project before I come. He says that the student was fired because he had a very bad character and also was working on other research projects and not the project he was assigned to (but that's his side of the story).
I have already taken my decision to talk to my bosses openly because I want to act professionally and be transparent. I don't know if they have deadlines or other related stuff to my project, so I don't want to cause them any other problem.
I feel I am totally worthless and stupid because as a postdoc this should have come easier on me. In fact I am thinking that if they throw me out after next week's meeting I will not ever come back to academia.
Do you have any other suggestion? Am I seeing it the right way?
EDIT: If I rephrase my question will you open it? I think it can be usefull also for other people.
UPDATE: In a couple months my contract expires and I have already a first draft of my paper! I guess it was very important that I had a PI that understood that I was freaking out and calming me down was the best strategy in order to help me with the research.