Oilboiler - give yourself a couple of years, maybe even three - it all depends on how much work your supervisors are giving you.
In my case, and with many fellow engineers I know, an engineer goes through the following evolution:
1. Starts out pretty confident, after all you graduated, have a great new job, and you are used to being the "senior" person around school. This ends after the first couple of days on the job.
2. For the first few months, feelings of Ohmygosh jump in every so often as you are given work and you feel like those around you are all focusing on your performance and, well, you'd better not screw up or everyone will shake their heads at your utter "green-ness"....you are the center of the universe in your own eyes, but in reality, most others don't really notice or don't care.
3. After stage 2 you settle down a bit, get into some semblance of a routine and begin to know how to do certain tasks. You still feel very uncertain at times and find yourself asking more and more questions.
4. After a couple of years, you can be given a variety of tasks but you still feel like the hammer will drop at any time when someone will require you to do something you have no clue how to approach. Still lots of questions of your supervisors - a very knee jerk reaction when you find yourself getting up from your desk to go ask - to make sure you're doing it right.
5. After three years or so you finally realize, as you are walking over to ask your supervisor another question, that, jeez, I know the answer and my supervisor doesn't really have a clue as to all the parameters involved in this particular problem. You turn around on your heels and go back to your desk....but still a little queazy.
6. At some point, you just swallow and DO YOUR JOB, feeling that if you don't know how to do it, then you will simply find out, research it, etc.
7. Even after 30 years you still have questions, still have doubts, but that old "will I be revealed to all as a phony" feeling is quite dim.