There are also many herbal remedies out there to normalise your cycle and increase fertility, such as licorice root (excellent also to nourish adrenals glands), vitex agnus castus (monkshood), black cohosh, saw palmetto, and ginseng (try siberian ginseng)as a general tonic which also improves sexual health.
Also try Yoga, there are many postures designed to help the reproductive organs. Get a book on Iyengar Yoga, there is one that shows all the specific asanas for fertility.
However, 4 months isn't too long yet, so I wouldn't get too worried, especially since you know that you're ovulating. And sometimes you just get pregnant when the time is right for you and the baby, so relax......