Three kids but want more

I have 3 wonderful children already and I want 1 or 2 more. I had no problems getting pregnant with them and went on birth control after my 3rd. I was on it for about 2 yrs and went off for a year to get pregnant and could not conceive and I tried everything. Has anyone experienced something like this or similar? I just turned 30 so age worries me if I wait much longer...