There are so many different things that could be a road block for you... I would suggest that you start with your obgyn. She may be able to do a few small, simple tests and can refer you and your partner to a specialist. Good Luck!!
I am also TTC from the last 3.5 yrs.I can better understand your feelings.I agree with happynifer. You should meet with fertility specialist.
Good Luck and lots of baby dust!!!
you need to start with seeing your doctor for a routine physical and routine blood testing. If all is well, then you should see a reproductive endocrinologist at a fertility center for fertility specific testing.
a good book to read is called "taking charge of your fertility" that discusses how your body works in plain language everyone can understand.
good luck!