How long were u TTC??

Ive been actively TTC for about five months now, I'm becoming impatient at this point. People have said to me if u want it to happen so bad it won't lol I already have had a daughter (she passed away) and I do have a son. I'm TTC with my children's father but I'm almost ready to give up :( I keep getting BFN. My ob/gyn said that in the first 3-4 months there's a 30% chance of conceiving. And by the 10th month It would be 90% chance