Hi, and thanks for your medical question on eHealth forum!
If you have been trying for a baby for 4 months then be patient. What is important is that you should try around your ovulation. The last 14 days of a cycle are fixed, that is after ovulation, if a woman does not conceive, she bleeds after 14 days. Some women get a spotting with ovulation and others get cramps. Almost everyone experiences an increase in white discharge around ovulation. There is always a rise in the basal body temperature (taken first thing in the morning before getting out of bed) around ovulation.
One can also calculate the date (approximate) by subtracting 14 from the average duration of cycle. So in a 28 day cycle the ovulation occurs on 14th day from start of menses, in a 30 day cycle the ovulation will occur on (30-14=16) 16th day of the cycle. The day is counted from the first day of the period. 2-3 days before this day to 2-3 days after the day is the most fertile period. Having intercourse during this time can result in pregnancy.
Keep an eye for these days and try. If you still do not conceive in 6-7 months time, then consult your gynecologist. Alternatively you can immediately consult a gynecologist and check if there is any problem. Hope this helps. Take care!