Dieting too harshly does affect ovulation, and so does being overweight. My sister tried for 8 years to get pg, even used fertility drugs. She was about 90 pounds overweight. She lost about 50 pounds and conceived without any treatment. You aren't that overweight, but some people are more sensitive to problems like that. It can't hurt to start eating healthier if you're concerned that it's a problem for you. I wouldn't however suggest doing anything drastic that limits any food groups, like Atkins, South Beach, Fat Smash, etc. Just try to count calories and eat healthier types of foods. There's nothing in doing that which would harm your fertility or a possible pregnancy you aren't aware of yet.
I can tell you from experience that weight issues can make pregnancy SO much more difficult. I gained 80 pounds with all 3 of mine. While I wasn't overweight at the start of any of my pregnancies, gaining so much weight definitely made me obese during and after. The heavier you are, the more uncomfortable you will be, the more strain put on your body, and labor will be much more difficult. I had to have c-sections, and I really believe that my weight played a part in that. Starting now before you get pg by eating more sensibly and starting an exercise program will not only possibly make you more fertile, but will make pregnancy easier and your recovery faster. Once you get pregnant, most doctors will tell you is NOT the time to make a drastic change to your body, like beginning a strenuous exercise routine that you aren't already used to, or trying to "diet" at all. You already have great intentions by planning to be as healthy as you can, and to try to meet new cravings and calorie demands with healthier choices. You are already on a much better track and have a better mindset than I did-because I made the horrible mistake of using pregnancing as an excuse to sit on the couch and eat twinkies and ho-ho's for 9 months