Am I able to conceive?

Hello everyone. You have probably heard this question before, so let me explain my situation. I'm 24 yrs old and I have a 4 yr old daughter. My husband and I now want to have another child. We've been trying for 6 mths now but with no success. A yr and a half ago, I had a copper IUD inserted. When my husband and I decided to have another child, I went to have it removed - so that was about 7 mths ago. since then, I haven't been able to get pregnant. Approximately 3 mths ago, I notice that my menstruation is very irregular - which is strange for me. I've been to the doctor and he told me that it coud be stress. He also said that I'm probably not timing my ovulation right so that's why I'm not pregnant yet. I have an appointment with my obgyn for the 23rd of this mth, but I'm anxious and very worried about the whole situation. I can't help but to think that the IUD I had in has something to do with this. Now, my mentruation is more than a wk late but both preg tsts that I did were neg.